Codebook design and structure for advanced wireless communication systems

Abstract

A base station capable of communicating with a user equipment (UE) includes a transceiver configured to transmit downlink signals containing first and second antenna numbers, first and second oversampling factors indicating respective oversampling rates in first and second dimensions for each beam group, first and second quantities of beams indicating respective quantities of beams in the first and second dimensions for each beam group, and first and second beam skip numbers indicating respective differences of leading beam indices of two adjacent beam groups in the first and second dimensions, receive uplink signals containing a plurality of precoding matrix indicators (PMIs) from the UE. Other embodiments including methods and UEs and methods are disclosed.

Claims

1. A user equipment (UE) capable of communicating with a base station, the UE comprising: a transceiver configured to: receive downlink signals indicating precoder codebook parameters, the downlink signal including: first and second quantities of antenna ports indicating respective quantities of antenna ports in first and second dimensions; first and second oversampling factors indicating respective oversampling factors for Discrete Fourier Transform (DFT) beams in the first and second dimensions; either at least one beam group configuration among a plurality of beam group configurations or first and second quantities of beams indicating respective quantities of beams in the first and second dimensions forming a beam group; and first and second beam skip numbers indicating respective differences of leading beam indices of two adjacent beam groups in the first and second dimensions; and a controller configured to: determine a precoder, using the received precoder codebook configuration; determine a plurality of precoding matrix indicators (PMIs) based on the received downlink signals; and cause the transceiver to transmit uplink signals containing the plurality of PMIs to the base station.

2. The UE of claim 1, wherein the transceiver is further configured to: receive first and second beam spacing numbers indicating a respective difference of two adjacent beam indices within each beam group in the first and second dimensions.

3. The UE of claim 2, wherein the transceiver is further configured to: receive first and second codebook restriction parameters indicating a restriction on at least one of beam skipping performed based on the first and second beam skip numbers, beam spacing performed based on the first and second beam spacing numbers, and beam grouping performed based on at least one beam group configuration in the first and second dimensions, wherein each codebook restriction parameter is in a bitmap format.

4. The UE of claim 1, wherein the transceiver is further configured to: receive first and second quantities of subset beams indicating respective quantities of subset beams in the first and second dimensions within each beam group of the configured codebook.

5. The UE of claim 1, wherein the transceiver is further configured to: receive a configuration number indicating one of a plurality of beam grouping schemes, each beam grouping scheme comprising a pattern of selected beams within each beam group of the configured codebook, wherein each beam grouping scheme has a different pattern of selected beams for different first and second quantities of subset beams.

6. The UE of claim 5, wherein the selected beams within each beam group are orthogonal to one another in at least one of the first and second dimensions.

7. The UE of claim 1, wherein the UE is configured with first and second dimension codebook parameters, and codebook restriction parameters via a higher-layer signaling.

8. A base station capable of communicating with a user equipment (UE), the base station comprising: a transmitter configured to: transmit downlink signals indicating precoder codebook parameters, the downlink signal including: first and second quantities of antenna ports indicating respective quantities of antenna ports in first and second dimensions; first and second oversampling factors indicating respective oversampling factors for c Discrete Fourier Transform (DFT) beams in the first and second dimensions; either at least one beam group configuration among a plurality of beam group configurations or first and second quantities of beams indicating respective quantities of beams in the first and second dimensions forming a beam group; and first and second beam skip numbers indicating respective differences of leading beam indices of two adjacent beam groups in the first and second dimensions; and a receiver configured to: receive uplink signals containing a plurality of precoding matrix indicators (PMIs) from the UE; and determine a precoder, using the received PMIs.

9. The base station of claim 8, wherein the transceiver transmitter is further configured to: transmit first and second beam spacing numbers indicating a respective difference of two adjacent beam indices within each beam group in the first and second dimensions.

10. The base station of claim 9, wherein the transmitter is further configured to: transmit first and second codebook restriction parameters indicating a restriction on at least one of beam skipping performed based on the first and second beam skip numbers, beam spacing performed based on the first and second beam spacing numbers, and beam grouping performed based on at least one beam group configuration in the first and second dimensions, wherein each codebook restriction parameter is in a bitmap format.

11. The base station of claim 8, wherein the transmitter is further configured to: transmit first and second quantities of subset beams indicating respective quantities of subset beams in the first and second dimensions within each beam group of the codebook.

12. The base station of claim 8, wherein the transmitter is further configured to: transmit a configuration number indicating one of a plurality of beam grouping schemes, each beam grouping scheme comprising a pattern of selected beams within each beam group of the codebook, wherein each beam grouping scheme has a different pattern of selected beams for different first and second quantities of subset beams.

13. The base station of claim 12, wherein the selected beams within each beam group are orthogonal to one another in at least one of first and second dimensions.

14. The base station of claim 8, wherein the base station transmits first and second dimension codebook parameters and codebook restriction parameters via a higher-layer signaling.

15. A method of operating a base station capable of communicating with a user equipment (UE), the method comprising: transmitting downlink signals indicating precoder codebook parameters, the downlink signal including: first and second quantities of antenna ports indicating respective quantities of antenna ports in first and second dimensions; first and second oversampling factors indicating respective oversampling factors for Discrete Fourier Transform (DFT) beams in the first and second dimensions; either at least one beam group configuration among a plurality of beam group configurations or first and second quantities of beams indicating respective quantities of beams in the first and second dimensions forming a beam group; and first and second beam skip numbers indicating respective differences of leading beam indices of two adjacent beam groups in the first and second dimensions; receiving uplink signals containing a plurality of precoding matrix indicators (PMIs) from the UE; and determining a precoder, using the received PMIs.

16. The method of claim 15, the method further comprising: transmitting first and second beam spacing numbers indicating a respective difference of two adjacent beam indices within each beam group in the first and second dimensions.

17. The method of claim 16, the method further comprising: transmitting first and second codebook restriction parameters indicating a restriction on at least one of beam skipping performed based on the first and second beam skip numbers, beam spacing performed based on the first and second beam spacing numbers, and beam grouping performed based on at least one beam group configuration in the first and second dimensions, wherein each codebook restriction parameter is in a bitmap format.

18. The method of claim 15, the method further comprising: transmitting first and second quantities of subset beams indicating respective quantities of subset beams in the first and second dimensions within each beam group of the codebook.

19. The method of claim 15, the method further comprising: transmitting a configuration number indicating one of a plurality of beam grouping schemes, each beam grouping scheme comprising a pattern of selected beams within each beam group of the codebook, wherein each beam grouping scheme has a different pattern of selected beams for different first and second quantities of subset beams.

20. The method of claim 19, wherein the selected beams within each beam group are orthogonal to one another.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) For a more complete understanding of the present disclosure and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which like reference numerals represent like parts:

(2) FIG. 1 illustrates an example wireless network according to this disclosure;

(3) FIGS. 2A and 2B illustrate example wireless transmit and receive paths according to this disclosure;

(4) FIG. 3A illustrates an example user equipment according to this disclosure;

(5) FIG. 3B illustrates an example enhanced NodeB (eNB) according to this disclosure;

(6) FIG. 4 illustrates logical port to antenna port mapping 400 that may be employed within the wireless communication system according to some embodiments of the current disclosure;

(7) FIGS. 5A to 5D illustrate antenna configurations and antenna numberings according to some embodiments of the present disclosure;

(8) FIG. 6 illustrates a precoding weight application to antenna configurations of FIGS. 5A to 5D for Numbering scheme 1;

(9) FIG. 7 illustrates a 4×4 dual-polarized antenna array 700 with antenna port (AP) indexing 1;

(10) FIG. 8 is a 4×4 dual-polarized antenna array 800 with antenna port indexing (AP) indexing 2;

(11) FIG. 9 illustrates another numbering of TX antenna elements 900 (or TXRU) according to embodiments of the present disclosure;

(12) FIG. 10 illustrates a beam grouping scheme corresponding to Scheme 1 in TABLE 1 according to embodiment of the present disclosure;

(13) FIG. 11 illustrates a beam grouping scheme corresponding to Scheme 2 in TABLE 1 according to the embodiments of the present disclosure;

(14) FIG. 12 illustrates a beam grouping scheme 1200 corresponding to Scheme 3 in TABLE 1 according to embodiments of the present disclosure;

(15) FIG. 13 illustrates a new codebook construction 1300 according to embodiments of the present disclosure;

(16) FIG. 14 illustrates another new codebook construction according to embodiments of the present disclosure;

(17) FIG. 15 illustrates a new codebook construction for P=32 antenna ports according to embodiments of the present disclosure;

(18) FIG. 16 shows example beam patterns according to embodiments of the present disclosure;

(19) FIG. 17 illustrates an alternate codebook construction in which two different vertical beams may be applied for the two polarizations according to the present disclosure;

(20) FIG. 18 illustrates PUCCH mode 1-1 submode 1 according to embodiments of the present disclosure;

(21) FIG. 19 illustrates an example UE elevation angle distribution in cellular wireless systems, in urban macro (UMa) and urban micro (UMi) cases;

(22) FIGS. 20 to 22 illustrate three examples of PUCCH mode 1-1 submode 1 according to embodiments of the present disclosure;

(23) FIG. 23 illustrates an example of PUCCH mode 1-1 submode x according to embodiments of the present disclosure;

(24) FIGS. 24 to 26 illustrates respective beam grouping schemes 1, 2 and 3 according to embodiments of the present disclosure;

(25) FIG. 27 illustrates a master codebook with example beam groups for N1=4 and N2=4 according to embodiments of the present disclosure;

(26) FIG. 28 illustrates the subset restriction on rank-1 i1 according to embodiments of the present disclosure;

(27) FIG. 29 illustrates the example beam groups in the master codebook after subset restriction according to the present disclosure;

(28) FIG. 30 illustrates the subset restriction 300 on rank-1 i2 according to the embodiments of the present disclosure;

(29) FIG. 31 illustrates a flowchart 3100 for UE operation for configuring parametrized codebook 3100 according to embodiments of the present disclosure;

(30) FIG. 32 illustrates a flowchart of the overall eNB and UE operation according to the parameterized codebook according to the present disclosure;

(31) FIG. 33 illustrates an example beam group type in which beams are adjacent in both dimensions according to the present disclosure;

(32) FIGS. 34A and 34B illustrate another example beam group types in which a beam group consists of orthogonal beam pairs in the first (horizontal) dimension, and adjacent beams in the second (vertical) dimension;

(33) FIG. 35 illustrates alternative rank-1 beam grouping schemes according to some embodiments of the present disclosure;

(34) FIG. 36 illustrate a beam combination to construct rank-2 master codebook according to some embodiments of the present disclosure;

(35) FIG. 37 illustrates rank-2 beam grouping schemes for rank-2 i2 according to some embodiments of the present disclosure;

(36) FIG. 38 illustrates a beam combination to construct rank-3 and rank-4 master codebooks according to some embodiments of the present disclosure;

(37) FIG. 39 illustrates grouping schemes for rank-3 and rank-4 i2 according to some embodiments of the present disclosure;

(38) FIG. 40 illustrates a beam combination to construct rank 5-8 beam combination master codebooks according to some embodiments of the present disclosure;

(39) FIG. 41 illustrates grouping schemes for rank 5-8 i2 according to some embodiments of the present disclosure;

(40) FIG. 42 illustrate a beam combination to construct a master codebook for rank-2 beam combinations according to embodiments of the present disclosure;

(41) FIG. 43 illustrates rank-2 beam grouping schemes according to some embodiments of the present disclosure;

(42) FIG. 44 illustrates beam grouping schemes for rank-3 and rank-4 i2 according to the present disclosure;

(43) FIG. 45 illustrates a beam combination to construct ranks 5-8 master codebooks according to some embodiments of the present disclosure;

(44) FIG. 46 illustrates beam grouping schemes for ranks 5-8 i2 indices according to the embodiments of the present disclosure;

(45) FIG. 47 illustrates beam grouping scheme or codebook subset selection on rank-2 i2 indices in terms of parameters L1 and L2, according to the embodiments of the present disclosure;

(46) FIG. 48 illustrates rank 3 and rank 4 beam grouping schemes according to embodiments of the present disclosure;

(47) FIG. 49 illustrates ranks 5 to 8 beam grouping schemes according to the present disclosure;

(48) FIG. 50 illustrates the master rank-2 codebook designed according to Design 1 according to the present disclosure;

(49) FIG. 51 illustrates the master rank-2 codebook designed according to Design 2 according to embodiments of the present disclosure;

(50) FIG. 52 illustrates beam grouping options for Config 1, Config 2, Config 3, and Config 4 according to the present disclosure; and

(51) FIG. 53 illustrates rank 2 beam pairs based on nested property with rank 1 beam according to embodiments of the present disclosure.

DETAILED DESCRIPTION

(52) FIGS. 1 through 53, discussed below, and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged wireless communication system.

(53) The following documents and standards descriptions are hereby incorporated by reference into the present disclosure as if fully set forth herein: (1) 3rd generation partnership project (3GPP) TS 36.211, “E-UTRA, Physical channels and modulation”, Release-12; (2) 3GPP TS 36.212, “E-UTRA, Multiplexing and channel coding”, Release-12; and (3) 3GPP TS 36.213, “E-UTRA, Physical layer procedures”, Release-12.

(54) FIG. 1 illustrates an example wireless network 100 according to this disclosure. The embodiment of the wireless network 100 shown in FIG. 1 is for illustration only. Other embodiments of the wireless network 100 could be used without departing from the scope of this disclosure.

(55) The wireless network 100 includes an eNodeB (eNB) 101, an eNB 102, and an eNB 103. The eNB 101 communicates with the eNB 102 and the eNB 103. The eNB 101 also communicates with at least one Internet Protocol (IP) network 130, such as the Internet, a proprietary IP network, or other data network.

(56) 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).

(57) The eNB 102 provides wireless broadband access to the network 130 for a first plurality of user equipments (UEs) within a coverage area 120 of the eNB 102. The first plurality of UEs includes a UE 111, which may be located in a small business (SB); a UE 112, which may be located in an enterprise (E); a UE 113, which may be located in a WiFi hotspot (HS); a UE 114, which may be located in a first residence (R); a UE 115, which may be located in a second residence (R); and a UE 116, which may be a mobile device (M) like a cell phone, a wireless laptop, a wireless PDA, or the like. The eNB 103 provides wireless broadband access to the network 130 for a second plurality of UEs within a coverage area 125 of the eNB 103. The second plurality of UEs includes the UE 115 and the UE 116. In some embodiments, one or more of the eNBs 101-103 may communicate with each other and with the UEs 111-116 using 5G, long-term evolution (LTE), LTE-A, WiMAX, or other advanced wireless communication techniques.

(58) Dotted lines show the approximate extents of the coverage areas 120 and 125, which are shown as approximately circular for the purposes of illustration and explanation only. It should be clearly understood that the coverage areas associated with eNBs, such as the coverage areas 120 and 125, 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.

(59) As described in more detail below, one or more of BS 101, BS 102 and BS 103 include 2D antenna arrays as described in embodiments of the present disclosure. In some embodiments, one or more of BS 101, BS 102 and BS 103 support the codebook design and structure for systems having 2D antenna arrays.

(60) Although FIG. 1 illustrates one example of a wireless network 100, various changes may be made to FIG. 1. For example, the wireless network 100 could include any number of eNBs and any number of UEs in any suitable arrangement. Also, the eNB 101 could communicate directly with any number of UEs and provide those UEs with wireless broadband access to the network 130. Similarly, each eNB 102-103 could communicate directly with the network 130 and provide UEs with direct wireless broadband access to the network 130. Further, the eNB 101, 102, and/or 103 could provide access to other or additional external networks, such as external telephone networks or other types of data networks.

(61) FIGS. 2A and 2B illustrate example wireless transmit and receive paths according to this disclosure. In the following description, a transmit path 200 may be described as being implemented in an eNB (such as eNB 102), while a receive path 250 may be described as being implemented in a UE (such as UE 116). However, it will be understood that the receive path 250 could be implemented in an eNB and that the transmit path 200 could be implemented in a UE. In some embodiments, the receive path 250 is configured to support the codebook design and structure for systems having 2D antenna arrays as described in embodiments of the present disclosure.

(62) The transmit path 200 includes a channel coding and modulation block 205, a serial-to-parallel (S-to-P) block 210, a size N Inverse Fast Fourier Transform (IFFT) block 215, a parallel-to-serial (P-to-S) block 220, an add cyclic prefix block 225, and an up-converter (UC) 230. The receive path 250 includes a down-converter (DC) 255, a remove cyclic prefix block 260, a serial-to-parallel (S-to-P) block 265, a size N Fast Fourier Transform (FFT) block 270, a parallel-to-serial (P-to-S) block 275, and a channel decoding and demodulation block 280.

(63) In the transmit path 200, the channel coding and modulation block 205 receives a set of information bits, applies coding (such as a low-density parity check (LDPC) coding), and modulates the input bits (such as with Quadrature Phase Shift Keying (QPSK) or Quadrature Amplitude Modulation (QAM)) to generate a sequence of frequency-domain modulation symbols. The serial-to-parallel block 210 converts (such as de-multiplexes) the serial modulated symbols to parallel data in order to generate N parallel symbol streams, where N is the IFFT/FFT size used in the eNB 102 and the UE 116. The size N IFFT block 215 performs an IFFT operation on the N parallel symbol streams to generate time-domain output signals. The parallel-to-serial block 220 converts (such as multiplexes) the parallel time-domain output symbols from the size N IFFT block 215 in order to generate a serial time-domain signal. The add cyclic prefix block 225 inserts a cyclic prefix to the time-domain signal. The up-converter 230 modulates (such as up-converts) the output of the add cyclic prefix block 225 to an RF frequency for transmission via a wireless channel. The signal may also be filtered at baseband before conversion to the RF frequency.

(64) A transmitted RF signal from the eNB 102 arrives at the UE 116 after passing through the wireless channel, and reverse operations to those at the eNB 102 are performed at the UE 116. The down-converter 255 down-converts the received signal to a baseband frequency, and the remove cyclic prefix block 260 removes the cyclic prefix to generate a serial time-domain baseband signal. The serial-to-parallel block 265 converts the time-domain baseband signal to parallel time domain signals. The size N FFT block 270 performs an FFT algorithm to generate N parallel frequency-domain signals. The parallel-to-serial block 275 converts the parallel frequency-domain signals to a sequence of modulated data symbols. The channel decoding and demodulation block 280 demodulates and decodes the modulated symbols to recover the original input data stream.

(65) Each of the eNBs 101-103 may implement a transmit path 200 that is analogous to transmitting in the downlink to UEs 111-116 and may implement a receive path 250 that is analogous to receiving in the uplink from UEs 111-116. Similarly, each of UEs 111-116 may implement a transmit path 200 for transmitting in the uplink to eNBs 101-103 and may implement a receive path 250 for receiving in the downlink from eNBs 101-103.

(66) Each of the components in FIGS. 2A and 2B can be implemented using only hardware or using a combination of hardware and software/firmware. As a particular example, at least some of the components in FIGS. 2A and 2B may be implemented in software, while other components may be implemented by configurable hardware or a mixture of software and configurable hardware. For instance, the FFT block 270 and the IFFT block 215 may be implemented as configurable software algorithms, where the value of size N may be modified according to the implementation.

(67) Furthermore, although described as using FFT and IFFT, this is by way of illustration only and should not be construed to limit the scope of this disclosure. Other types of transforms, such as Discrete Fourier Transform (DFT) and Inverse Discrete Fourier Transform (IDFT) functions, could be used. It will be appreciated that the value of the variable N may be any integer number (such as 1, 2, 3, 4, or the like) for DFT and IDFT functions, while the value of the variable N may be any integer number that is a power of two (such as 1, 2, 4, 8, 16, or the like) for FFT and IFFT functions.

(68) Although FIGS. 2A and 2B illustrate examples of wireless transmit and receive paths, various changes may be made to FIGS. 2A and 2B. For example, various components in FIGS. 2A and 2B could be combined, further subdivided, or omitted and additional components could be added according to particular needs. Also, FIGS. 2A and 2B are meant to illustrate examples of the types of transmit and receive paths that could be used in a wireless network. Any other suitable architectures could be used to support wireless communications in a wireless network.

(69) FIG. 3A illustrates an example UE 116 according to this disclosure. The embodiment of the UE 116 illustrated in FIG. 3A is for illustration only, and the UEs 111-115 of FIG. 1 could have the same or similar configuration. However, UEs come in a wide variety of configurations, and FIG. 3A does not limit the scope of this disclosure to any particular implementation of a UE.

(70) The UE 116 includes an antenna 305, a radio frequency (RF) transceiver 310, transmit (TX) processing circuitry 315, a microphone 320, and receive (RX) processing circuitry 325. The UE 116 also includes a speaker 330, a main processor 340, an input/output (I/O) interface (IF) 345, a keypad 350, a display 355, and a memory 360. The memory 360 includes a basic operating system (OS) program 361 and one or more applications 362.

(71) The RF transceiver 310 receives, from the antenna 305, an incoming RF signal transmitted by an eNB of the network 100. The RF transceiver 310 down-converts the incoming RF signal to generate an intermediate frequency (IF) or baseband signal. The IF or baseband signal is sent to the RX processing circuitry 325, which generates a processed baseband signal by filtering, decoding, and/or digitizing the baseband or IF signal. The RX processing circuitry 325 transmits the processed baseband signal to the speaker 330 (such as for voice data) or to the main processor 340 for further processing (such as for web browsing data).

(72) The TX processing circuitry 315 receives analog or digital voice data from the microphone 320 or other outgoing baseband data (such as web data, e-mail, or interactive video game data) from the main processor 340. The TX processing circuitry 315 encodes, multiplexes, and/or digitizes the outgoing baseband data to generate a processed baseband or IF signal. The RF transceiver 310 receives the outgoing processed baseband or IF signal from the TX processing circuitry 315 and up-converts the baseband or IF signal to an RF signal that is transmitted via the antenna 305.

(73) The main processor 340 can include one or more processors or other processing devices and execute the basic OS program 361 stored in the memory 360 in order to control the overall operation of the UE 116. For example, the main processor 340 could control the reception of forward channel signals and the transmission of reverse channel signals by the RF transceiver 310, the RX processing circuitry 325, and the TX processing circuitry 315 in accordance with well-known principles. In some embodiments, the main processor 340 includes at least one microprocessor or microcontroller.

(74) The main processor 340 is also capable of executing other processes and programs resident in the memory 360, such as operations for channel quality measurement and reporting for systems having 2D antenna arrays as described in embodiments of the present disclosure as described in embodiments of the present disclosure. The main processor 340 can move data into or out of the memory 360 as required by an executing process. In some embodiments, the main processor 340 is configured to execute the applications 362 based on the OS program 361 or in response to signals received from eNBs or an operator. The main processor 340 is also coupled to the I/O interface 345, which provides the UE 116 with the ability to connect to other devices such as laptop computers and handheld computers. The I/O interface 345 is the communication path between these accessories and the main controller 340.

(75) The main processor 340 is also coupled to the keypad 350 and the display unit 355. The operator of the UE 116 can use the keypad 350 to enter data into the UE 116. The display 355 may be a liquid crystal display or other display capable of rendering text and/or at least limited graphics, such as from web sites.

(76) The memory 360 is coupled to the main processor 340. Part of the memory 360 could include a random access memory (RAM), and another part of the memory 360 could include a Flash memory or other read-only memory (ROM).

(77) Although FIG. 3A illustrates one example of UE 116, various changes may be made to FIG. 3A. For example, various components in FIG. 3A could be combined, further subdivided, or omitted and additional components could be added according to particular needs. As a particular example, the main processor 340 could be divided into multiple processors, such as one or more central processing units (CPUs) and one or more graphics processing units (GPUs). Also, while FIG. 3A illustrates the UE 116 configured as a mobile telephone or smartphone, UEs could be configured to operate as other types of mobile or stationary devices.

(78) FIG. 3B illustrates an example eNB 102 according to this disclosure. The embodiment of the eNB 102 shown in FIG. 3B is for illustration only, and other eNBs of FIG. 1 could have the same or similar configuration. However, eNBs come in a wide variety of configurations, and FIG. 3B does not limit the scope of this disclosure to any particular implementation of an eNB. It is noted that eNB 101 and eNB 103 can include the same or similar structure as eNB 102.

(79) As shown in FIG. 3B, the eNB 102 includes multiple antennas 370a-370n, multiple RF transceivers 372a-372n, transmit (TX) processing circuitry 374, and receive (RX) processing circuitry 376. In certain embodiments, one or more of the multiple antennas 370a-370n include 2D antenna arrays. The eNB 102 also includes a controller/processor 378, a memory 380, and a backhaul or network interface 382.

(80) The RF transceivers 372a-372n receive, from the antennas 370a-370n, incoming RF signals, such as signals transmitted by UEs or other eNBs. The RF transceivers 372a-372n down-convert the incoming RF signals to generate IF or baseband signals. The IF or baseband signals are sent to the RX processing circuitry 376, which generates processed baseband signals by filtering, decoding, and/or digitizing the baseband or IF signals. The RX processing circuitry 376 transmits the processed baseband signals to the controller/processor 378 for further processing.

(81) The TX processing circuitry 374 receives analog or digital data (such as voice data, web data, e-mail, or interactive video game data) from the controller/processor 378. The TX processing circuitry 374 encodes, multiplexes, and/or digitizes the outgoing baseband data to generate processed baseband or IF signals. The RF transceivers 372a-372n receive the outgoing processed baseband or IF signals from the TX processing circuitry 374 and up-converts the baseband or IF signals to RF signals that are transmitted via the antennas 370a-370n.

(82) The controller/processor 378 can include one or more processors or other processing devices that control the overall operation of the eNB 102. For example, the controller/processor 378 could control the reception of forward channel signals and the transmission of reverse channel signals by the RF transceivers 372a-372n, the RX processing circuitry 376, and the TX processing circuitry 324 in accordance with well-known principles. The controller/processor 378 could support additional functions as well, such as more advanced wireless communication functions. For instance, the controller/processor 378 can perform the blind interference sensing (BIS) process, such as performed by a BIS algorithm, and decodes the received signal subtracted by the interfering signals. Any of a wide variety of other functions could be supported in the eNB 102 by the controller/processor 378. In some embodiments, the controller/processor 378 includes at least one microprocessor or microcontroller.

(83) The controller/processor 378 is also capable of executing programs and other processes resident in the memory 380, such as a basic OS. The controller/processor 378 is also capable of supporting channel quality measurement and reporting for systems having 2D antenna arrays as described in embodiments of the present disclosure. In some embodiments, the controller/processor 378 supports communications between entities, such as web RTC. The controller/processor 378 can move data into or out of the memory 380 as required by an executing process.

(84) The controller/processor 378 is also coupled to the backhaul or network interface 335. The backhaul or network interface 382 allows the eNB 102 to communicate with other devices or systems over a backhaul connection or over a network. The interface 382 could support communications over any suitable wired or wireless connection(s). For example, when the eNB 102 is implemented as part of a cellular communication system (such as one supporting 5G, LTE, or LTE-A), the interface 382 could allow the eNB 102 to communicate with other eNBs over a wired or wireless backhaul connection. When the eNB 102 is implemented as an access point, the interface 382 could allow the eNB 102 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). The interface 382 includes any suitable structure supporting communications over a wired or wireless connection, such as an Ethernet or RF transceiver.

(85) The memory 380 is coupled to the controller/processor 325. Part of the memory 330 could include a RAM, and another part of the memory 380 could include a Flash memory or other ROM. In certain embodiments, a plurality of instructions, such as a BIS algorithm is stored in memory. The plurality of instructions are configured to cause the controller/processor 378 to perform the BIS process and to decode a received signal after subtracting out at least one interfering signal determined by the BIS algorithm.

(86) As described in more detail below, the transmit and receive paths of the eNB 102 (implemented using the RF transceivers 372a-372n, TX processing circuitry 374, and/or RX processing circuitry 376) support communication with aggregation of FDD cells and TDD cells.

(87) Although FIG. 3B illustrates one example of an eNB 102, various changes may be made to FIG. 3B. For example, the eNB 102 could include any number of each component shown in FIG. 3. As a particular example, an access point could include a number of interfaces 382, and the controller/processor 378 could support routing functions to route data between different network addresses. As another particular example, while shown as including a single instance of TX processing circuitry 374 and a single instance of RX processing circuitry 376, the eNB 102 could include multiple instances of each (such as one per RF transceiver).

(88) Logical Port to Antenna Port Mapping

(89) FIG. 4 illustrates logical port to antenna port mapping 400 that may be employed within the wireless communication system according to some embodiments of the current disclosure. The embodiment of the port mapping illustrated in FIG. 4 is for illustration only. However, port mappings come in a wide variety of configurations, and FIG. 4 does not limit the scope of this disclosure to any particular implementation of a port mapping.

(90) FIG. 4 illustrates logical port to antenna port mapping, according to some embodiments of the current disclosure. In the figure, Tx signals on each logical port is fed into an antenna virtualization matrix (e.g., of a size M×1), output signals of which are fed into a set of M physical antenna ports. In some embodiments, M corresponds to a total number or quantity of antenna elements on a substantially vertical axis. In some embodiments, M corresponds to a ratio of a total number or quantity of antenna elements to S, on a substantially vertical axis, wherein M and S are chosen to be a positive integer.

(91) Antenna Configurations and Antenna Numbering

(92) FIGS. 5A to 5D illustrate antenna configurations and antenna numberings according to one embodiments of the present disclosure. The embodiments shown in FIGS. 5A to 5D are for illustration only. Other embodiments could be used without departing from the scope of the present disclosure.

(93) In all the four antenna configurations of FIGS. 5A to 5D, a cross pol (or X-pol) antenna array is considered, in which a pair of antenna elements in a same physical location are polarized in two distinct angles, e.g., +45 degrees and −45 degrees.

(94) FIGS. 5A and 5B are antenna configurations with 16 CSI-RS ports, comprising 8 pairs of x-pol antenna elements placed in a 2D antenna panel. The 8 pairs can be placed in 2×4 (FIG. 5A) or 4×2 manner (FIG. 5B) on horizontal and vertical dimensions.

(95) FIGS. 5C and 5D are antenna configurations with 12 CSI-RS ports, comprising 6 pairs of x-pol antenna elements placed in a 2D antenna panel. The 6 pairs can be placed in 2×3 (FIG. 5C) or 3×2 manner (FIG. 5D) on horizontal and vertical dimensions.

(96) Antenna Number Assignment

(97) In FIGS. 5A to 5D, antennas are indexed with integer numbers, 0, 1, . . . , 15 for 16-port configurations (FIGS. 5A and 5B), and 0, . . . , 11 for 12-port configurations (FIGS. 5C and 5D).

(98) In wide arrays (such as 12-port config A and 16-port config A), antenna numbers are assigned as follows. Consecutive numbers are assigned for all the antenna elements for a first polarization, and proceed to a second polarization. And, for a given polarization, Numbering scheme 1: consecutive numbers are assigned for a first row with progressing one edge to another edge, and proceed to a second row; and Numbering scheme 2: consecutive numbers are assigned for a first column with progressing one edge to another edge, and proceed to a second column.

(99) For example, in FIG. 5A, antenna numbers 0-7 are assigned for a first polarization, and 8-15 are assigned for a second polarization; and antenna numbers 0-3 are assigned for a first row and 4-7 are assigned for a second row.

(100) Antenna numbers in tall arrays (such as 12-port config B and 16-port config B) are obtained by simply rotating the wide antenna arrays (such as 12-port config A and 16-port config A) by 90 degrees.

(101) PMI Feedback Precoder Generation according to the Antenna Numbering

(102) In some embodiments, when a UE is configure with 12 or 16 port CSI-RS for a CSI-RS resource, the UE is configured to report a PMI feedback precoder according to the antenna numbers in FIGS. 5A to 5D. A rank-1 precoder, W.sub.m,n,p, which is an N.sub.CSIRS×1 vector, to be reported by the UE has the following form:

(103) $W_{m,n,p}={\left[\begin{array}{cccc}{w}_0& w_1& \mathrm{.Math.}& w_{N_{\mathrm{CSIRS}}-1}\end{array}\right]}^t=\frac{1}{\sqrt{N_{\mathrm{CSIRS}}}}\left[\begin{array}{c}{v}_m.Math.u_n\\ {\phi }_p\left(v_{m^{\prime }}.Math.u_{n^{ \prime }}\right)\end{array}\right],$
wherein: N.sub.CSIRS=number of configured CSI-RS ports in the CSI-RS resource, e.g., 12, 16, etc; u.sub.n is a N×1 oversampled DFT vector for a second dimension, whose oversampling factor is S.sub.N; v.sub.m is a M×1 oversampled DFT vector for a first dimension, whose oversampling factor is S.sub.M; The dimension assignment can be done with N≧M according to numbering scheme 1 in FIGS. 4A to 4D, with (N,M) ε {(4,2), (4,3), (2,2)}; alternatively, the dimension assignment can be done with N≦M with swapping the role of columns and rows, with (N,M) ε {(2,4), (3,4), (2,2)} according to numbering scheme 2 in FIGS. 4A to 4C; and φ.sub.p is a co-phase, e.g., in a form of

(104) $e^{\frac{2\pi p}{4}},$
p=0,1,2,3.

(105) Here, example set of oversampling factors that can be configured for S.sub.N and S.sub.M are {2,4,8}; and m, m′ ε {0,1, . . . , S.sub.MM}, and n, n′ ε {0,1, . . . , S.sub.NN}. In a special case, m=m′ and n=n′.

(106) FIG. 6 illustrates a precoding weight application to antenna configurations of FIGS. 5A to 5D for numbering scheme 1.

(107) When any of 16-port config A and B for Numbering scheme 1 is used at the eNB with configuring N.sub.CSIRS=16 to the UE, a submatrix v.sub.mu.sub.n of W.sub.m,n,p corresponds to a precoder applied on 8 co-pol elements, whose antenna numbers are 0 through 7. Given the antenna configuration, M=2 and N=4 should be configured for v.sub.m and u.sub.n.

(108) If 16-port config A is used, u.sub.n is a 4×1 vector representing a horizontal DFT beam and v.sub.m is a 2×1 vector representing a vertical DFT beam. If 16-port config B is used, u.sub.n is a 4×1 vector representing a vertical DFT beam and v.sub.m is a 2×1 vector representing a horizontal DFT beam.

(109) With 12 or 16-port configurations, v.sub.m can be written as

(110) $v_m={\left[\begin{array}{cc}1& e^{j\frac{2\pi m}{M^{\prime }}}\end{array}\right]}^t={\left[\begin{array}{cc}1& e^{j\frac{2\pi m}{{\mathrm{MS}}_M}}\end{array}\right]}^t.$
With 16-port configurations, u.sub.n can be written as:

(111) $\begin{array}{c}{u}_n={\left[\begin{array}{cccc}1& e^{j\frac{2\pi n}{N^{\prime }}}& e^{j\frac{4\pi m}{N^{\prime }}}& e^{j\frac{6\pi m}{N^{\prime }}}\end{array}\right]}^t\\ ={\left[\begin{array}{cccc}1& e^{j\frac{2\pi n}{{\mathrm{NS}}_N}}& e^{j\frac{4\pi m}{{\mathrm{NS}}_N}}& e^{j\frac{6\pi m}{{\mathrm{NS}}_N}}\end{array}\right]}^t.\end{array}$

(112) With 12-port configurations, u.sub.n can be written as:

(113) $\begin{array}{c}{u}_n={\left[\begin{array}{ccc}1& e^{j\frac{2\pi n}{N^{\prime }}}& e^{j\frac{4\pi m}{N^{\prime }}}\end{array}\right]}^t\\ ={\left[\begin{array}{ccc}1& e^{j\frac{2\pi n}{{\mathrm{NS}}_N}}& e^{j\frac{4\pi m}{{\mathrm{NS}}_N}}\end{array}\right]}^t.\end{array}$

(114) Precoding weights to be applied to antenna port numbers 0 through 3 are u.sub.n, and the precoding weights to be applied to antenna ports 4 through 7 are

(115) $u_n{e}^{j\frac{2\pi m}{{\mathrm{MS}}_M}}$
with an appropriate power normalization factor. Similarly, precoding weights to be applied to antenna port numbers 8 through 11 are u.sub.n′, and the precoding weights to be applied to antenna ports 12 through 15 are

(116) $u_{n^{\prime }}{e}^{j\frac{2\pi m^{\prime }}{{\mathrm{MS}}_M}}$
with an appropriate power normalization factor. This method of precoding weight application for Numbering scheme 1 is illustrated in FIGS. 5A to 5D. Note that the method is also applicable to Numbering scheme 2.

(117) FIG. 7 illustrates a 4×4 dual-polarized antenna array 700 with antenna port (AP) indexing 1 and FIG. 8 is the same 4×4 dual-polarized antenna array 800 with antenna port indexing (AP) indexing 2.

(118) In certain embodiments, each labelled antenna element is logically mapped onto a single antenna port. In general, one antenna port can correspond to multiple antenna elements (physical antennas) combined via a virtualization. This 4×4 dual polarized array can then be viewed as 16×2=32-element array of elements. The vertical dimension (consisting of 4 rows) facilitates elevation beamforming in addition to the azimuthal beamforming across the horizontal dimension (consisting of 4 columns of dual polarized antennas). MIMO precoding in Rel.12 LTE standardization (per TS36.211 sections 6.3.4.2 and 6.3.4.4; and TS36.213 section 7.2.4) was largely designed to offer a precoding gain for one-dimensional antenna array. While fixed beamforming (i.e. antenna virtualization) can be implemented across the elevation dimension, it is unable to reap the potential gain offered by the spatial and frequency selective nature of the channel.

(119) FIG. 9 illustrates another numbering of TX antenna elements 900 (or TXRU) according to embodiments of the present disclosure. The embodiment shown in FIG. 9 is for illustration only. Other embodiments could be used without departing from the scope of the present disclosure.

(120) In certain embodiments, eNB is equipped with 2D rectangular antenna array (or TXRUs), comprising M rows and N columns with P=2 polarized, wherein each element (or TXRU) is indexed with (m, n, p), and m=0, . . . , M-1, n=0, . . . , N-1, p=0, . . . , P-1, as illustrated in FIG. 9 with M=N=4. When the example shown in FIG. 7 represents a TXRU array, a TXRU can be associated with multiple antenna elements. In one example (1-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 in FIG. 9. In later embodiments, (M,N) is sometimes denoted as (N.sub.H, N.sub.V) or (N.sub.1, N.sub.2).

(121) 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.

(122) CSI-RS and CSI Feedback Configuration

(123) In some embodiments, a UE is configured with a CSI-RS configuration via higher layer, configuring Q antenna ports—antenna ports A(1) through A(Q). The UE is further configured with CSI reporting configuration via higher layer in association with the CSI-RS configuration.

(124) 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.sub.1 and N.sub.2, which respectively indicates a first number of antenna ports for a first dimension, and a second number of antenna ports for a second dimension, wherein Q=N.sub.1.Math.N.sub.2.

(125) One example method of indicating the CSI-RS decomposition (or component PMI port configuration) is described below.

(126) TABLE-US-00001 CSIRS decomposition When Q = 8, (N.sub.1, N.sub.2) ∈ {(2, 4), (4, 2)}. information or When Q = 16, (N.sub.1, N.sub.2) ∈ {(2, 8), (4, 4), (8, 2)}. Component PMI port When Q = 32, (N.sub.1, N.sub.2) ∈ {(8, 4), (4, 8)}. configuration

(127) Another example method of indicating the PMI reporting decomposition is to explicitly configure Q and N.sub.1, and implicitly configure N.sub.2.

(128) TABLE-US-00002 Component PMI port Q . . . positive even number, e.g., selected from configuration {1, 2, 4, . . . , 32} N.sub.1 . . . positive even number, e.g., selected from {1, 2, 4, . . . , 16} N.sub.2 = Q/N.sub.1 . . . implicitly derived out of explicitly configured N and N.sub.1.

(129) Another example method of indicating the PMI reporting decomposition is to explicitly configure N.sub.1 and N.sub.2, and implicitly configure Q.

(130) TABLE-US-00003 Component PMI port N.sub.1 . . . positive even number, e.g., selected from configuration {1, 2, 4, . . . , 16} N.sub.2 . . . positive even number, e.g., selected from {1, 2, 4, . . . , 16} Q = N.sub.1 .Math. N.sub.2 . . . implicitly derived out of explicitly configured N.sub.1 and N.sub.2.

(131) Another example method of indicating the PMI reporting decomposition is to explicitly configure M, N, and P, and implicitly configure Q.

(132) TABLE-US-00004 Component PMI port M . . . positive even number, e.g., selected from configuration {1, 2, 4, . . . , 16} N . . . positive even number, e.g., selected from {1, 2, 4, . . . , 16} P . . . either 1 or 2 Q = M .Math. N .Math. P . . . implicitly derived out of explicitly configured M, N, and P.

(133) When the UE is configured with (N.sub.1, N.sub.2), the UE calculates CQI with a composite precoder constructed with two-component codebooks, N.sub.1-Tx codebook (codebook 1) and N.sub.2-Tx codebook (codebook 2). When W.sub.1 and W.sub.2 are respectively are precoders of codebook 1 and codebook 2, the composite precoder (of size P×(rank)) is the (columnwise) Kronecker product of the two, W=W.sub.1W.sub.2. If PMI reporting is configured, the UE will report at least two component PMI corresponding to selected pair of W.sub.1 and W.sub.2.

(134) In one method, either W.sub.1 or W.sub.2 is further decomposed according to the double codebook structure. For example, W.sub.1 is further decomposed into:

(135) $W_1\left(n,m\right)=\frac{1}{p_1}\left[\begin{array}{c}{v}_m\\ {\phi }_n{v}_m\end{array}\right]$
if rank 1; and

(136) $W_1\left(n,m,m^{\prime }\right)=\frac{1}{p_2}\left[\begin{array}{cc}{v}_m& v_{m^{\prime }}\\ {\phi }_n{v}_m& -{\phi }_n{v}_{m^{\prime }}\end{array}\right]$
if rank 2,
wherein p.sub.1 and p.sub.2 are normalization factors to make total transmission power 1, v.sub.m is an m-th DFT vector out of a (N.sub.1/2)-Tx DFT codebook with oversampling factor o.sub.1, and φ.sub.n is a co-phase. Furthermore, the index m, m′, n determines the precoder W.sub.1.

(137) If the transmission rank is one (or number of transmission layers is one), then CQI will be derived with

(138) 0$W=W_1.Math.W_2=\frac{1}{p_1}\left[\begin{array}{c}{v}_m.Math.W_2\\ {\phi }_n{v}_m.Math.W_2\end{array}\right];$
and if the transmission rank is two, then CQI will be derived with

(139) $W=W_1.Math.W_2{|}_{\mathrm{columnwiseKP}}=\frac{1}{p_2}\left[\begin{array}{cc}{v}_m.Math.W_2& v_{m^{\prime }}.Math.W_2\\ {\phi }_n{v}_m.Math.W_2& -{\phi }_n{v}_{m^{\prime }}.Math.W_2\end{array}\right].$

(140) In one example of this method, N.sub.1=8 and N.sub.2=4, and the TXRUs (or the antenna ports) are numbered according to FIG. 8. In this case, W.sub.1 is further decomposed into:

(141) $W_1\left(n,m\right)=\frac{1}{p_1}\left[\begin{array}{c}{v}_m\\ {\phi }_n{v}_m\end{array}\right]$
if rank 1; and

(142) $W_1\left(n,m,m^{\prime }\right)=\frac{1}{p_2}\left[\begin{array}{cc}{v}_m& v_{m^{\prime }}\\ {\phi }_n{v}_m& -{\phi }_n{v}_{m^{\prime }}\end{array}\right]$
if rank 2,
wherein v.sub.m is an m-th DFT vector out of a 4-Tx DFT codebook with oversampling factor 8; and

(143) ${\phi }_n=e^{j\frac{2\pi n}{4}}.$
Furthermore, with one transmission layer, CQI will be derived with precoder

(144) $W=W_1.Math.W_2=\frac{1}{\sqrt{8}}\left[\begin{array}{c}{v}_m.Math.W_2\\ {\phi }_n{v}_m.Math.W_2\end{array}\right];$
and with two transmission layer, CQI will be derived with precoder

(145) $W=W_1.Math.W_2{|}_{\mathrm{columnwiseKP}}=\frac{1}{4}\left[\begin{array}{cc}{v}_m.Math.W_2& v_{m^{\prime }}.Math.W_2\\ {\phi }_n{v}_m.Math.W_2& -{\phi }_n{v}_{m^{\prime }}.Math.W_2\end{array}\right].$

(146) In another method, both W.sub.1 and W.sub.2 are further decomposed according to the double codebook structure with two stages. The first stage codebook is used to represent WB and long-term channel, and the second stage codebook is used to represent SB and short-term channel. For example, W.sub.1 and W.sub.2 can be decomposed as W.sub.1=W.sub.1.sup.(1)W.sub.1.sup.(2) and W.sub.2=W.sub.2.sup.(1)W.sub.2.sup.(2), respectively, where: W.sub.1.sup.(1) and W.sub.2.sup.(1) are the first stage codebooks; W.sub.1.sup.(2) and W.sub.2.sup.(2) are the second stage codebooks; W.sub.1 comprises of DFT vectors out of a (N.sub.1/2)-Tx DFT codebook with oversampling factor o.sub.1, where the first stage codebook W.sub.1.sup.(1) corresponds to a set of fixed number L.sub.1 of uniformly-spaced beams, and the second stage codebook W.sub.2.sup.(2) corresponds to selecting one beam out of L.sub.1 beams and applying a x-pol co-phase φ.sub.n; and W.sub.2 comprises of DFT vectors out of a (N.sub.2)-Tx DFT codebook with oversampling factor o.sub.2, where the first stage codebook W.sub.2.sup.(1) corresponds to a set of fixed number L.sub.2 of uniformly-spaced beams, and the second stage codebook W.sub.2.sup.(2) corresponds to selecting one beam out of L.sub.2 beams;

(147) In a special case, uniformly-spaced beams are consecutively-spaced beams.

(148) A beam grouping scheme is defined in terms of two groups of parameters, one group per dimension. A group of parameters for dimension d comprises at least one of the following parameters: a number of antenna ports N.sub.d.sup..Math.; an oversampling factor o.sub.d.sup..Math.; a skip number s.sub.d.sup..Math.; a beam offset number f.sub.d.sup..Math.; and a number of beams L.sub.d.

(149) In some embodiments, a beam group indicated by a first PMI i.sub.1,d of dimension d (corresponding to W.sub.d.sup.(1)), is determined based upon these five parameters.

(150) The total number of beams is N.sub.d.sup..Math. o.sub.d.sup..Math.; and the beams are indexed by an integer m.sub.d, wherein beam m.sub.d, v.sub.m.sub.d, corresponds to a precoding vector

(151) $v_{m_d}={\left[\begin{array}{cccc}1& e^{j\frac{2\pi m_d}{o_d{N}_d}}& \mathrm{.Math.}& e^{j\frac{2\pi m_d\left(N_d-1\right)}{o_d{N}_d}}\end{array}\right]}^t,$
m.sub.d=0, . . . , N.sub.d.sup..Math. o.sub.d−1.

(152) The first PMI of the dimension d, i.sub.1,d, i.sub.1,d=0, . . . , N.sub.d.sup..Math. o.sub.d/s.sub.d−1, can indicate any of L.sub.d beams indexed by: m.sub.d=f.sub.d+s.sub.d.Math.i.sub.1,d,f.sub.d+s.sub.d.Math.i.sub.1,d+1, . . . , f.sub.d+s.sub.d.Math.i.sub.1,d+L.sub.d−1. These L.sub.d beams are referred to as a beam group in dimension d.

(153) In some embodiments, a UE may be configured via higher layers (e.g., RRC) with at least one of these five parameters, wherein a subset of parameters not configured in the same configuration may have been pre-configured at the UE.

(154) In one example, a UE is configured via higher layers with an oversampling factor o.sub.2 for the second dimension in an RRC configuration, who is also pre-configured with all the other parameters: For the first dimension: N.sub.1=8, o.sub.1=8, s.sub.1=2, f.sub.1=0, and L.sub.1=4; and For the second dimension: N.sub.2=4, s.sub.2=2, f.sub.1=0, and L.sub.1=4;

(155) TABLE-US-00005 Oversampling factor o.sub.2 for the second dimension Eumerated {1, 2, 4}

(156) In this case, the beams in the beam group indicated by the first PMI of the first dimension, i.sub.1,1, is:

(157) $v_{m_1}={\left[\begin{array}{cccc}1& e^{j\frac{2\pi m_1}{32}}& e^{j\frac{4\pi m_1}{32}}& e^{j\frac{6\pi m_1}{32}}\end{array}\right]}^t,$
m.sub.1=2i.sub.1,1, 2i.sub.1,1+1, 2i.sub.1,1+2, 2i.sub.1,1+3; and the beams in the beam group indicated by the first PMI of the second dimension, i.sub.1,2, is:

(158) $v_{m_2}={\left[\begin{array}{cccc}1& e^{j\frac{2\pi m_2}{4o_2}}& e^{j\frac{4\pi m_2}{4o_2}}& e^{j\frac{6\pi m_2}{4o_2}}\end{array}\right]}^t,$
m.sub.2=2i.sub.1,2, 2i.sub.1,2+1, 2i.sub.1,2+2, 2i.sub.1,2+3.

(159) In a special case of o.sub.2=1, there is only one group of size L.sub.2=4, which is:

(160) 0$v_{m_2}={\left[\begin{array}{cccc}1& e^{j\frac{2\pi m_2}{4}}& e^{j\frac{4\pi m_2}{4}}& e^{j\frac{6\pi m_2}{4}}\end{array}\right]}^t,$
m.sub.2=0, 1, 2, 3. In this special case, the UE does not (need to) report i.sub.1,2.

(161) In another example, a UE is configured via higher layers with two numbers of beams, L.sub.1 and L.sub.2 respectively for the first and the second dimension in an RRC configuration, who is also pre-configured with all the other parameters. For the first dimension: N.sub.1=8, o.sub.1=8, s.sub.1=2, f.sub.1=0; and for the second dimension: N.sub.2=4, o.sub.2=4, s.sub.2=2, f.sub.1=0.

(162) TABLE-US-00006 Number of beams for the first dimension L.sub.1 Eumerated {1, 2, 4} Number of beams for the second dimension L.sub.1 Eumerated {1, 2, 4}

(163) In this case, the beams in the beam group indicated by the first PMI of the first dimension, i.sub.1,1, is:

(164) $v_{m_1}={\left[\begin{array}{cccc}1& e^{j\frac{2\pi m_1}{32}}& e^{j\frac{4\pi m_1}{32}}& e^{j\frac{6\pi m_1}{32}}\end{array}\right]}^t,$
m.sub.1=2i.sub.1,1, . . . , 2i.sub.1,1+L.sub.1−1; and the beams in the beam group indicated by the first PMI of the second dimension, i.sub.1,2, is:

(165) $v_{m_2}={\left[\begin{array}{cccc}1& e^{j\frac{2\pi m_2}{16}}& e^{j\frac{4\pi m_2}{16}}& e^{j\frac{6\pi m_2}{16}}\end{array}\right]}^t,$
m.sub.2=2i.sub.1,2, . . . , 2i.sub.1,2i.sub.1,2+L.sub.2−1.

(166) In some embodiments, N.sub.1=8 and N.sub.2=4, and the TXRUs (or the antenna ports) are numbered according to FIG. 8. Three illustrative beam grouping schemes, referred to as Scheme 1, Scheme 2, and Scheme 3, according to the double codebook structure are shown in FIGS. 10, 11 and 12, and the related parameters are listed in TABLE 1.

(167) TABLE-US-00007 TABLE 1 Parameters for three example beam grouping schemes A first A second oversampling A first number of oversampling A second number factor o.sub.1 for the beams L.sub.1 for the factor o.sub.2 for the of beams L.sub.2 for the first dimension first dimension second dimension second dimension Scheme 1 8 4 4 1 Scheme 2 8 4 4 2 Scheme 3 8 2 4 2

(168) In these schemes, a horizontal oversampling factor o.sub.1=8 is considered for W.sub.1.sup.(1) codebook and a vertical oversampling factor o.sub.2=4 is considered for W.sub.2.sup.(1) codebook. Hence, total number of beams for W.sub.1.sup.(1) codebook is

(169) $\frac{N_1{o}_1}{P}=32,$
and total number of beams for W.sub.2.sup.(1) codebook is N.sub.2o.sub.2=16. FIGS. 10 to 12 illustrate these 16×32 3D beams constructed by Kronecker product of each beam vector in W.sub.1.sup.(1) codebook and each beam vector in W.sub.2.sup.(1) codebook as a 16×32 grid, wherein each square correspond to a beam.

(170) FIG. 10 illustrates a beam grouping scheme corresponding to Scheme 1 in TABLE 1 according to embodiment of the present disclosure. The embodiment shown in FIG. 10 is for illustration only. Other embodiments could be used without departing from the scope of the present disclosure.

(171) In Scheme 1, W.sub.1.sup.(1) codebook is a set of uniformly-spaced 4 DFT beams (L.sub.1=4). In the figure, a first, a second, and a third beam groups are illustrated. The first group comprises beams corresponding to beam grids (h,v)=(0,0), (1,0), (2,0), and (3,0), where h and v refer to horizontal and vertical grid indices, respectively. The second group comprises beams corresponding to beam grids (h,v)=(2,0), (3,0), (4,0), and (5,0). The beam groups with v=0 can be similarly constructed, and total number of beam groups with v=0 is 16. The third group comprises beams corresponding to beam grids (h,v)=(0,1), (1,1), (2,1), and (3,1). Continuing similarly through horizontal and vertical beam directions, 16×16=256 beam groups are constructed. A beam group can be indicated by a log 2(256)=8 bit field. Note that in Scheme 1, W.sub.1.sup.(1) corresponds to the first stage codebook in Rel. 10 8-Tx double codebook, and W.sub.2.sup.(1) codebook is the set of single DFT beams (L.sub.2=1).

(172) FIG. 11 illustrates a beam grouping scheme 1100 corresponding to Scheme 2 in TABLE 1 according to the embodiments of the present disclosure. The embodiment shown in FIG. 11 is for illustration only. Other embodiments could be used without departing from the scope of the present disclosure.

(173) In Scheme 2, W.sub.1.sup.(1) codebook is a set of uniformly-spaced 4 DFT beams (L.sub.1=4) and W.sub.2.sup.(1) codebook is a set of uniformly-spaced 2 DFT beams (L.sub.1=2). In the figure, a first, a second, and a third beam groups are illustrated. The first group comprises beams corresponding to beam grids (h,v)=(0,0), (1,0), (2,0), (3,0), (0,1), (1,1), (2,1), and (3,1). The second group comprises beams corresponding to beam grids (h,v)=(2,0), (3,0), (4,0), (5,0), (2,1), (3,1), (4,1), and (5,1). The beam groups with v=0 and 1 can be similarly constructed, and total number of beam groups with v=0 and 1 is 16. The third group comprises beams corresponding to beam grids (h,v)=(0,2), (1,2), (2,2), (3,2), (0,3), (1,3), (2,3), and (3,3). Continuing similarly through horizontal and vertical beam directions, 16×8=128 beam groups are constructed. A beam group can be indicated by a log 2(128)=7 bit field. Note that in Scheme 2, W.sub.1.sup.(1) corresponds to the first stage codebook in Rel. 10 8-Tx double codebook.

(174) FIG. 12 illustrates a beam grouping scheme 1200 corresponding to Scheme 3 in TABLE 1 according to embodiments of the present disclosure. The embodiment shown in FIG. 12 is for illustration only. Other embodiments could be used without departing from the scope of the present disclosure.

(175) In Scheme 3, both W.sub.1.sup.(1) and W.sub.2.sup.(1) are sets of uniformly-spaced 2 DFT beams (L.sub.1=L.sub.2=2). In the figure, a first, a second, and a third beam groups are illustrated. The first group comprises beams corresponding to beam grids (h,v)=(0,0), (1,0), (0,1), and (1,1). The second group comprises beams corresponding to beam grids (h,v)=(2,0), (3,0), (2,1), and (3,1). The beam groups with v=0 and 1 can be similarly constructed, and total number of beam groups with v=0 and 1 is 16. The third group comprises beams corresponding to beam grids (h,v)=(0,2), (1,2), (0,3), and (1,3). Continuing similarly through horizontal and vertical beam directions, 16×8=128 beam groups are constructed. A beam group can be indicated by a log 2(128)=7 bit field.

(176) It should be noted that these codebooks are for illustration only. The method is applicable to other kinds of double codebooks.

(177) In some embodiments, PMI indices corresponding to W.sub.1.sup.(1) and W.sub.2.sup.(1) are WB and long-term and that corresponding to W.sub.1.sup.(2) and W.sub.2.sup.(2) are SB and short-term. The PMI feedback payload to indicate PMI indices for the three schemes is shown in below TABLE 2. Both WB and SB components of the feedback overhead can be decomposed into two, one for azimuth and the other for elevation.

(178) WB components: in all three schemes, a 4-bit feedback is needed to report azimuth component of the PMI index (H-PMI) corresponding to W.sub.1.sup.(1). In Scheme 1, if V-PMI is configured as a WB component, then V-PMI is reported as a 4 bit information, which corresponds to W.sub.2.sup.(1). Otherwise no WB V-PMI is reported (i.e., 0 bits for W.sub.2.sup.(1)). In both Schemes 2 and 3, V-PMI is reported as a 3-bit information, which corresponds to W.sub.2.sup.(1).

(179) SB components: in all three schemes, a 2-bit feedback is needed to report the co-phase value. To report azimuth component of the PMI index (H-PMI) corresponding to W.sub.1.sup.(2), a 2-bit indication is used in Schemes 1 and 2, and a 1-bit indication is used in Scheme 3. For elevation component of the PMI index (V-PMI) corresponding to W.sub.2.sup.(2), a 4-bit indication is used in Scheme 1 if SB V-PMI is configured, and a 1-bit feedback is used in Schemes 2 and 3.

(180) TABLE-US-00008 TABLE 2 Feedback overhead of different beam grouping schemes SB components WB components Co- Azimuth Elevation Azimuth Elevation phasing (bits) (bits) (bits) (bits) (bits) Scheme 1 4 4 if WB 2 4 if SB 2 V-PMI is V-PMI is configured; configured; 0 otherwise 0 otherwise Scheme 2 4 3 2 1 2 Scheme 3 4 3 1 1 2

(181) In some embodiments, the UE is configured with one first-stage codebook selected from multiple candidate first-stage codebooks, in which each first stage codebook is associated with a set of parameters defining a single beam grouping scheme such as Schemes 1, 2, and 3 in TABLE 1. In one example, a beam grouping scheme may be configured via higher-layers (e.g, RRC) according to the below; or a preferred beam grouping scheme may be reported by the UE.

(182) TABLE-US-00009 Beam grouping scheme for the Eumerated {Scheme 1, Scheme 2, first stage codebook Scheme 3} . . . related to schemes in TABLE 1

(183) In some embodiments, the UE is configured with one first-stage codebook selected from multiple candidate first-stage codebooks where each first stage codebook is associated with multiple beam grouping schemes wherein example beam grouping schemes are shown in TABLE 1. In this case, the UE can more flexibly select SB PMI. For example, a UE may be configured to report a first PMI based upon the first-stage codebook, comprising beam groups constructed by Schemes 1 and 2. For this configuration, a new information element (IE) that can be configured in the higher-layer (e.g., RRC) can be designed as shown below, which indicates which of schemes 1, 2 and 3 are used for constructing beam groups for first stage codebook construction.

(184) TABLE-US-00010 Selected beam grouping Eumerated {Schemes 1&2, Schemes 1&3, schemes for the first stage Schemes 2&3} . . . related to schemes in codebook TABLE 1

(185) In this case, the total number of beam groups indicated by W.sub.1.sup.(1) and W.sub.2.sup.(1) is determined as sum of numbers of beam groups indicated by the two schemes. For example, when schemes 1 and 3 are chosen, the total number of beam groups is 256+128=384. A UE may report a one-bit selected beam group index information, as well as the first PMI i.sub.1,1 and i.sub.1,2 for the two dimensions; in this case, the first PMI is interpreted differently according to the reported beam group index.

(186) In some embodiments, a UE is configured with a CSI-RS configuration via higher layer, configuring two resources, wherein a first resource is used for CSI-RS transmissions of N.sub.1 antenna ports—antenna ports A(1) through A(N.sub.1), and a second resource is used for CSI-RS transmissions of N.sub.2 antenna ports—antenna ports B(1) through B(N.sub.2).

(187) When the UE is configured with (N.sub.1, N.sub.2), the UE calculates CQI with a composite precoder constructed with two-component codebooks, N.sub.1-Tx codebook (codebook 1) and N.sub.2-Tx codebook (codebook 2). When W.sub.1 and W.sub.2 are respectively are precoders of codebook 1 and codebook 2, the composite precoder (of size P×(rank), wherein P=N.sub.1.Math.N.sub.2) is the Kronecker product of the two, W=W.sub.1W.sub.2. If PMI reporting is configured, the UE will report two component PMI corresponding to selected pair of W.sub.1 and W.sub.2. The signals formed with the composite precoder is assumed to be transmitted on antenna ports C(1), . . . , C(P) for the purpose of deriving CQI index. The UE may also assume that reference signals on antenna ports C(1), . . . , C(P) are constructed by a Kronecker product of reference signals on A(1), . . . , A(N.sub.1) and reference signals on B(1), . . . , B(N.sub.2). In other words: [C(1), . . . , C(P)].sup.t=[A(1), . . . , A(N.sub.1)].sup.t[B(1), . . . , B(N.sub.2)].sup.t.

(188) Relation of Composite Precoder to Antenna Ports

(189) In some embodiments, for the purpose of deriving CQI index, and PMI and RI (if configured), the UE may assume the following:

(190) The PDSCH signals on antenna ports {7, . . . , 6+ν} would result in signals equivalent to corresponding symbols transmitted on antenna ports {15, . . . , 14+P}, as given by

(191) $\left[\begin{array}{c}{y}^{\left(15\right)}\left(i\right)\\ \mathrm{.Math.}\\ y^{\left(14+P\right)}\left(i\right)\end{array}\right]=W\left(i\right)\left[\begin{array}{c}{x}^{\left(0\right)}\left(i\right)\\ \mathrm{.Math.}\\ x^{\left(\upsilon -1\right)}\left(i\right)\end{array}\right],$
where x(i)=[x.sup.(0) (i) . . . x.sup.(ν−1) (i)].sup.T is a vector of symbols from the layer mapping in subclause 6.3.3.2 of 3GPP TS 36.211, P is the number of antenna ports of the associated CSI-RS resource, and if P=1, W(i) is 1, otherwise W(i), of size P×ν, is the precoding matrix corresponding to the reported PMI applicable to x(i). The corresponding PDSCH signals transmitted on antenna ports {15 . . . 14+P} would have a ratio of EPRE to CSI-RS EPRE equal to the ratio given in subclause 3GPP TS 36.213.

(192) 8-Tx Double Codebook

(193) TABLE 3 and TABLE 4 are codebooks for rank-1 and rank-2 (1-layer and 2-layer) CSI reporting for UEs configured with 8 Tx antenna port transmissions. To determine a CW for each codebook, two indices, i.e., i.sub.1 and i.sub.2 have to be selected. In these precoder expressions, the following two variables are used:
φ.sub.n=e.sup.jπn/2
v.sub.m=[1 e.sup.j2πm/32 e.sup.j4πm/32 e.sup.j6πm/32].sup.T.Math.

(194) TABLE-US-00011 TABLE 3 Codebook for 1-layer CSI reporting using antenna ports 15 to 22 i.sub.2 i.sub.1 0 1 2 3 4 5 6 7 0-15 W.sub.2i.sub.1.sub.,0.sup.(1) W.sub.2i.sub.1.sub.,1.sup.(1) W.sub.2i.sub.1.sub.,2.sup.(1) W.sub.2i.sub.1.sub.,3.sup.(1) W.sub.2i.sub.1.sub.+1,0.sup.(1) W.sub.2i.sub.1.sub.+1,1.sup.(1) W.sub.2i.sub.1.sub.+1,2.sup.(1) W.sub.2i.sub.1.sub.+1,3.sup.(1) i.sub.2 i.sub.1 8 9 10 11 12 13 14 15 0-15 W.sub.2i.sub.1.sub.+2,0.sup.(1) W.sub.2i.sub.1.sub.+2,1.sup.(1) W.sub.2i.sub.1.sub.+2,2.sup.(1) W.sub.2i.sub.1.sub.+2,3.sup.(1) W.sub.2i.sub.1.sub.+3,0.sup.(1) W.sub.2i.sub.1.sub.+3,1.sup.(1) W.sub.2i.sub.1.sub.+3,2.sup.(1) W.sub.2i.sub.1.sub.+3,3.sup.(1) $\mathrm{where}{W}_{m,n}^{\left(1\right)}=\frac{1}{\sqrt{8}}\left[\begin{array}{c}{v}_m\\ {\phi }_n{v}_m\end{array}\right],$

(195) If the most recently reported RI=1, m and n are derived with the two indices i.sub.1 and i.sub.2 according to TABLE 3, resulting in a rank-1 precoder,

(196) $W_{m,n}^{\left(1\right)}=\frac{1}{\sqrt{8}}\left[\begin{array}{c}{v}_m\\ {\phi }_n{v}_m\end{array}\right].$

(197) TABLE-US-00012 TABLE 4 Codebook for 2-layer CSI reporting using antenna ports 15 to 22 i.sub.2 i.sub.1 0 1 2 3 0-15 W.sub.2i.sub.1.sub.,2i.sub.1.sub.,0.sup.(2) W.sub.2i.sub.1.sub.,2i.sub.1.sub.,1.sup.(2) W.sub.2i.sub.1.sub.+1,2i.sub.1.sub.+1,0.sup.(2) W.sub.2i.sub.1.sub.+1,2i.sub.1.sub.+1,1.sup.(2) i.sub.2 i.sub.1 4 5 6 7 0-15 W.sub.2i.sub.1.sub.+2,2i.sub.1.sub.+2,0.sup.(2) W.sub.2i.sub.1.sub.+2,2i.sub.1.sub.+2,1.sup.(2) W.sub.2i.sub.1.sub.+3,2i.sub.1.sub.+3,0.sup.(2) W.sub.2i.sub.1.sub.+3,2i.sub.1.sub.+3,1.sup.(2) i.sub.2 i.sub.1 8 9 10 11 0-15 W.sub.2i.sub.1.sub.,2i.sub.1.sub.+1,0.sup.(2) W.sub.2i.sub.1.sub.,2i.sub.1.sub.+1,1.sup.(2) W.sub.2i.sub.1.sub.+1,2i.sub.1.sub.+2,0.sup.(2) W.sub.2i.sub.1.sub.+1,2i.sub.1.sub.+2,1.sup.(2) i.sub.2 i.sub.1 12 13 14 15 0-15 W.sub.2i.sub.1.sub.,2i.sub.1.sub.+3,0.sup.(2) W.sub.2i.sub.1.sub.,2i.sub.1.sub.+3,1.sup.(2) W.sub.2i.sub.1.sub.+1,2i.sub.1.sub.+3,0.sup.(2) W.sub.2i.sub.1.sub.+1,2i.sub.1.sub.+3,1.sup.(1) $\mathrm{where}{W}_{m,m^{\prime },n}^{\left(2\right)}=\frac{1}{4}\left[\begin{array}{cc}{v}_m& v_{m^{\prime }}\\ {\phi }_n{v}_m& -{\phi }_n{v}_{m^{\prime }}\end{array}\right]$

(198) If the most recently reported RI=2, m, m′ and n are derived with the two indices i.sub.1 and i.sub.2 according to TABLE 4, resulting in a rank-2 precoder,

(199) $W_{m,m^{\prime },n}^{\left(2\right)}=\frac{1}{4}\left[\begin{array}{cc}{v}_m& v_{m^{\prime }}\\ {\phi }_n{v}_m& -{\phi }_n{v}_{m^{\prime }}\end{array}\right].$
It is noted that W.sub.m,m′,n.sup.(2) is constructed such that it can be used for two different types of channel conditions that facilitate a rank-2 transmission.

(200) One subset of the codebook associated with i.sub.2={0, 1, . . . , 7} comprises codewords with m=m′, or the same beams (v.sub.m) are used for constructing the rank-2 precoder:

(201) $W_{m,m,n}^{\left(2\right)}=\frac{1}{4}\left[\begin{array}{cc}{v}_m& v_m\\ {\phi }_n{v}_m& -{\phi }_n{v}_m\end{array}\right].$
In this case, the two columns in the 2-layer precoder are orthogonal (i.e., [v.sub.m φ.sub.nv.sub.m].sup.H.Math.[v.sub.m−φ.sub.nv.sub.m]=0), owing to the different signs applied to φ.sub.n for the two columns. These rank-2 precoders are likely to be used for those UEs that can receive strong signals along two orthogonal channels generated by the two differently polarized antennas.

(202) FIG. 13 illustrates a new codebook construction 1300 according to embodiments of the present disclosure. The embodiment shown in FIG. 13 is for illustration only. Other embodiments could be used without departing from the scope of the present disclosure.

(203) In the embodiment, the new codebook construction is constructed for P=16 antenna ports comprising N.sub.1=8 and N.sub.2=2. For each group of APs corresponding to each row (i.e., {0, 1, . . . 7} and {8, 9, . . . , 15}, the channels are quantized with two indices i.sub.1,1 and i.sub.2,1, according to the 8-Tx double codebook. It is noted that the antenna (TXRU) numbering system in this example is aligned with FIG. 4A.

(204) A co-phasing vector to apply for the two rows is constructed with a new index k, and is equal to

(205) 0$V_k^{\left(1\right)}=\left[\begin{array}{c}1\\ u_k\end{array}\right].$
The resulting precoders W.sub.m,n,k.sup.(1) and W.sub.m,m′,n,k.sup.(2) when the most recently reported RI is 1 and 2 are:

(206) $W_{m,n,k}^{\left(1\right)}=\frac{1}{\sqrt{2}}\left[\begin{array}{c}{W}_{m,n}^{\left(1\right)}\\ u_k{W}_{m,n}^{\left(1\right)}\end{array}\right]$
if RI=1;

(207) $W_{m,m^{\prime },n,k}^{\left(2\right)}=\frac{1}{\sqrt{2}}\left[\begin{array}{c}{W}_{m,m^{\prime },n}^{\left(2\right)}\\ u_k{W}_{m,m^{\prime },n}^{\left(2\right)}\end{array}\right]$
if RI=2.

(208) It is noted that the precoders when the most recently reported RI is >2 can also be similarly constructed with applying a co-phasing vector. Case 1. (RI=1) Substituting

(209) $W_{m,n}^{\left(1\right)}=\frac{1}{\sqrt{8}}\left[\begin{array}{c}{v}_m\\ {\phi }_n{v}_m\end{array}\right]$
to

(210) $W_{m,n,k}^{\left(1\right)}=\frac{1}{\sqrt{2}}\left[\begin{array}{c}{W}_{m,n}^{\left(1\right)}\\ u_k{W}_{m,n}^{\left(1\right)}\end{array}\right],$
we obtain:

(211) $W_{m,n,k}^{\left(1\right)}\left(=V_k^{\left(1\right)}.Math.W_{m,n}^{\left(1\right)}\right)=\frac{1}{\sqrt{2}}\left[\begin{array}{c}{W}_{m,n}^{\left(1\right)}\\ u_k{W}_{m,n}^{\left(1\right)}\end{array}\right]=\frac{1}{4}\left[\begin{array}{c}{v}_m\\ {\phi }_n{v}_m\\ u_k{v}_m\\ {\phi }_n{u}_k{v}_m\end{array}\right].$

(212) Case 2. (RI=2) Substituting

(213) $W_{m,m^{\prime },n}^{\left(2\right)}=\frac{1}{4}\left[\begin{array}{cc}{v}_m& v_{m^{\prime }}\\ {\phi }_n{v}_m& -{\phi }_n{v}_{m^{\prime }}\end{array}\right]$
to

(214) $W_{m,m^{\prime },n,k}^{\left(2\right)}=\frac{1}{\sqrt{2}}\left[\begin{array}{c}{W}_{m,m^{\prime },n}^{\left(2\right)}\\ u_k{W}_{m,m^{\prime },n}^{\left(2\right)}\end{array}\right],$
we obtain:

(215) $W_{m,m^{\prime },n,k}^{\left(2\right)}\left(=V_k^{\left(1\right)}.Math.W_{m,m^{\prime },n}^{\left(2\right)}\right)=\frac{1}{\sqrt{2}}\left[\begin{array}{c}{W}_{m,m^{\prime },n}^{\left(2\right)}\\ u_k{W}_{m,m^{\prime },n}^{\left(2\right)}\end{array}\right]=\frac{1}{\sqrt{32}}\left[\begin{array}{cc}{v}_m& v_{m^{\prime }}\\ {\phi }_n{v}_m& -{\phi }_n{v}_{m^{\prime }}\\ u_k{v}_m& u_k{v}_{m^{\prime }}\\ {\phi }_n{u}_k{v}_m& -{\phi }_n{u}_k{v}_{m^{\prime }}\end{array}\right],$
where it is clarified that W.sub.m,m′,n,k.sup.(2) is indeed a Kronecker product of V.sub.k.sup.(1) and W.sub.m,m′,n.sup.(2).

(216) In one method, u.sub.k=e.sup.jπk/2, k=0,1,2,3, which is uniformly sampling the range of [0, 2π]. In this case, the rank-1 and rank-2 precoders are constructed as:

(217) $W_{m,n,k}^{\left(1\right)}=\frac{1}{4}\left[\begin{array}{c}{v}_m\\ e^{\frac{j\pi n}{2}}{v}_m\\ e^{\frac{j\pi k}{2}}{v}_m\\ e^{\frac{j\pi \left(n+k\right)}{2}}{v}_m\end{array}\right]\mathrm{and}$$W_{m,m^{\prime },n,k}^{\left(2\right)}=\frac{1}{\sqrt{32}}\left[\begin{array}{cc}{v}_m& v_{m^{\prime }}\\ e^{\frac{j\pi n}{2}}{v}_m& -e^{\frac{j\pi n}{2}}{v}_{m^{\prime }}\\ e^{\frac{j\pi k}{2}}{v}_m& e^{\frac{j\pi k}{2}}{v}_{m^{\prime }}\\ e^{\frac{j\pi \left(n+k\right)}{2}}{v}_m& -e^{\frac{j\pi \left(n+k\right)}{2}}{v}_{m^{\prime }}\end{array}\right].$

(218) In another method, u.sub.k=e.sup.jπk/4, k=0,1,2,3, which is uniformly sampling the range of [0, π]. This method is motivated by the fact that it would be sufficient to consider the range of [0, π] for quantizing the elevation (or zenith) angle, when azimuth angle spans [0, 2π] In this case, the rank-1 and rank-2 precoders are constructed as:

(219) 0$W_{m,n,k}^{\left(1\right)}=\frac{1}{4}\left[\begin{array}{c}{v}_m\\ e^{\frac{\mathrm{j\pi }n}{2}}{v}_m\\ e^{\frac{\mathrm{j\pi }k}{4}}{v}_m\\ e^{\frac{\mathrm{j\pi }\left(2n+k\right)}{4}}{v}_m\end{array}\right]\mathrm{and}$$W_{m,m^{\prime },n,k}^{\left(2\right)}=\frac{1}{\sqrt{32}}\left[\begin{array}{cc}{v}_m& v_{m^{\prime }}\\ e^{\frac{jn}{2}}{v}_m& -e^{\frac{j\pi n}{2}}{v}_{m^{\prime }}\\ e^{\frac{j\pi k}{4}}{v}_m& e^{\frac{j\pi k}{4}}{v}_{m^{\prime }}\\ e^{\frac{j\pi \left(2n+k\right)}{4}}{v}_m& -e^{\frac{j\pi \left(2n+k\right)}{4}}{v}_{m^{\prime }}\end{array}\right].$

(220) FIG. 14 illustrates another new codebook construction according to embodiments of the present disclosure. The embodiment shown in FIG. 14 is for illustration only. Other embodiments could be used without departing from the scope of the present disclosure.

(221) The codebook construction is the same as FIG. 13, except for the second column of the composite 16-Tx rank-2 precoder. According to this construction, the rank-2 precoder matrix is:

(222) $W_{m,m^{\prime },n,k}^{\left(2\right)}=\frac{1}{\sqrt{2}}\left[\begin{array}{c}\frac{1}{4}\left[\begin{array}{cc}{v}_m& v_{m^{\prime }}\\ {\phi }_n{v}_m& -{\phi }_n{v}_{m^{\prime }}\end{array}\right]\\ \frac{1}{4}\left[\begin{array}{cc}{u}_k{v}_m& -u_k{v}_{m^{\prime }}\\ {\phi }_n{u}_k{v}_m& {\phi }_n{u}_k{v}_{m^{\prime }}\end{array}\right]\end{array}\right]=\frac{1}{\sqrt{32}}\left[\begin{array}{cc}{v}_m& v_{m^{\prime }}\\ {\phi }_n{v}_m& -{\phi }_n{v}_{m^{\prime }}\\ u_k{v}_m& -u_k{v}_{m^{\prime }}\\ {\phi }_n{u}_k{v}_m& {\phi }_n{u}_k{v}_{m^{\prime }}\end{array}\right],$
where u.sub.k=e.sup.jπk/2, k=0,1,2,3 or u.sub.k=e.sup.jπk/4, k=0,1,2,3.

(223) FIG. 15 illustrates a new codebook construction for P=32 antenna ports comprising N.sub.1=8 and N.sub.2=4, according to embodiments of the present disclosure. The embodiment shown in FIG. 15 is for illustration only. Other embodiments could be used without departing from the scope of the present disclosure.

(224) The codebook is constructed under the same principle as FIG. 13. In this case, the co-phasing to be applied to the four rows is a 4×1 vector, V.sub.k.sup.(1)=[1 u.sub.k u.sub.2k u.sub.3k].sup.t, where u.sub.k=e.sup.jπk/2,k=0,1,2,3 or u.sub.k=e.sup.jπk/4,k=0,1,2,3. In this case, the rank-1 and rank-2 precoder is constructed as:

(225) $W_{m,n,k}^{\left(1\right)}\left(=V_k^{\left(1\right)}.Math.W_{m,n}^{\left(1\right)}\right)=\frac{1}{\sqrt{2}}\left[\begin{array}{c}{W}_{m,n}^{\left(1\right)}\\ u_k{W}_{m,n}^{\left(1\right)}\\ u_{2k}{W}_{m,n}^{\left(1\right)}\\ u_{3k}{W}_{m,n}^{\left(1\right)}\end{array}\right];$$W_{m,m^{\prime },n,k}^{\left(2\right)}\left(=V_k^{\left(1\right)}.Math.W_{m,m^{\prime },n}^{\left(2\right)}\right)=\frac{1}{\sqrt{2}}\left[\begin{array}{c}{W}_{m,m^{\prime },n}^{\left(2\right)}\\ u_k{W}_{m,m^{\prime },n}^{\left(2\right)}\\ u_{2k}{W}_{m,m^{\prime },n}^{\left(2\right)}\\ u_{3k}{W}_{m,m^{\prime },n}^{\left(2\right)}\end{array}\right].$

(226) Similarly, a new codebook can be constructed according to the same principle as in FIG. 13 and FIG. 15, for arbitrary numbers of N.sub.1 and N.sub.2; W.sub.m,n,k.sup.(1) and W.sub.m,m′,n,k.sup.(2) will comprise (N.sub.2×1) block matrices where each block corresponds to u.sub.kW.sub.m,n.sup.(1), k=0,1,2, . . . , N.sub.2; and u.sub.k=e.sup.jπk/N.sup.2.

(227) FIG. 16 shows example beam patterns constructed with [1 u.sub.k u.sub.2k u.sub.3k].sup.t and u.sub.k=e.sup.jπk/4,k=0,1,2,3, where antennas are spaced apart by 1.28λ, in the vertical domain. The figure shows that the elevation angle range of 90° to 115° are well-covered, the range of which corresponds to typical user elevation angle distribution.

(228) Polarization-Specific V Beams

(229) FIG. 17 illustrates an alternate codebook construction 1700 in which two different vertical beams may be applied for the two polarizations according to the present disclosure. The embodiment shown in FIG. 17 is for illustration only. Other embodiments could be used without departing from the scope of the present disclosure.

(230) In this exemplary figure, we have P=16 antenna ports comprising N.sub.1=8 and N.sub.2=2. For each group of APs corresponding to each row (i.e., {0, 1, . . . 7} and {8, 9, . . . , 15}, the channels are quantized with two indices i.sub.1 and i.sub.2, according to the 8-Tx double codebook. It is noted that the antenna (TXRU) numbering system in this example is aligned with FIG. 4A.

(231) Two co-phasing vectors or vertical beams to apply for the two rows are constructed with two new indices k.sub.1 and k.sub.2, and are equal to

(232) $V_{k_1}^{\left(1\right)}=\left[\begin{array}{c}1\\ u_{k_1}\end{array}\right]\mathrm{and}{V}_{k_2}^{\left(1\right)}=\left[\begin{array}{c}1\\ u_{k_2}\end{array}\right].$
The first vertical beam V.sub.k.sub.1.sup.(1) is applied to antenna ports with one polarization, shown as solid lines, and the second vertical beam V.sub.k.sub.2.sup.(1) is applied to antenna ports with other polarization, shown as dashed lines. Note that the proposed idea is applicable to rank 2 (RI=2). The resulting precoders W.sub.m,n,k.sub.1.sub.,k.sub.2.sup.(1) and W.sub.m,m′,n,k.sub.1.sub.,k.sub.2.sup.(2) when the most recently reported RI is 1 and 2 are:
Case 1. (RI=1):

(233) $W_{m,n,k_1,k_2}^{\left(1\right)}=\frac{1}{4}\left[\begin{array}{c}{v}_m\\ {\phi }_n{v}_m\\ u_{k_1}{v}_m\\ {\phi }_n{u}_{k_2}{v}_m\end{array}\right].$
Case 2. (RI=2):

(234) $W_{m,m^{\prime },n,k_1,k_2}^{\left(2\right)}=\frac{1}{\sqrt{32}}\left[\begin{array}{cc}{v}_m& v_{m^{\prime }}\\ {\phi }_n{v}_m& -{\phi }_n{v}_{m^{\prime }}\\ u_{k_1}{v}_m& u_{k_1}{v}_{m^{\prime }}\\ {\phi }_n{u}_{k_2}{v}_m& -{\phi }_n{u}_{k_2}{v}_{m^{\prime }}\end{array}\right],$
where it is clarified that W.sub.m,n,k.sub.1.sub.,k.sub.2.sup.(1) is indeed a concatenation of two Kronecker product, one for each polarization, i.e. KP (V.sub.k.sub.1.sup.(1), v.sub.m) and KP (V.sub.k.sub.2.sup.(1),φ.sub.nv.sub.m),

(235) It is noted that the precoders when the most recently reported RI is >2 can also be similarly constructed with applying two vertical co-phasing vectors.

(236) In one method, for both l=1,2, u.sub.k.sub.1=e.sup.jπk.sup.1.sup./2, k.sub.1=0,1,2,3, which is uniformly sampling the range of [0, 2πc]. In this case, the rank-1 and rank-2 precoders are constructed as:

(237) $W_{m,n,k_1,k_2}^{\left(1\right)}=\frac{1}{4}\left[\begin{array}{c}{v}_m\\ e^{\frac{j\pi n}{2}}{v}_m\\ e^{\frac{j\pi k_1}{2}}{v}_m\\ e^{\frac{j\pi \left(n+k_2\right)}{2}}{v}_m\end{array}\right]\mathrm{and}$$W_{m,m^{\prime },n,k_1,k_2}^{\left(2\right)}=\frac{1}{\sqrt{32}}\left[\begin{array}{cc}{v}_m& v_{m^{\prime }}\\ e^{\frac{j\pi n}{2}}{v}_m& -e^{\frac{j\pi n}{2}}{v}_{m^{\prime }}\\ e^{\frac{j\pi k_1}{2}}{v}_m& e^{\frac{j\pi k_1}{2}}{v}_{m^{\prime }}\\ e^{\frac{j\pi \left(n+k_2\right)}{2}}{v}_m& -e^{\frac{j\pi \left(n+k_2\right)}{2}}{v}_{m^{\prime }}\end{array}\right].$

(238) In another method, for both l=1,2, u.sub.k.sub.1=e.sup.jπk.sup.1.sup./4, k.sub.1=0,1,2,3, which is uniformly sampling the range of [0, π]. This method is motivated by the fact that it would be sufficient to consider the range of [0, π] for quantizing the elevation (or zenith) angle, when azimuth angle spans [0, 2π] In this case, the rank-1 and rank-2 precoders are constructed as:

(239) $W_{m,n,k_1,k_2}^{\left(1\right)}=\frac{1}{4}\left[\begin{array}{c}{v}_m\\ e^{\frac{j\pi n}{2}}{v}_m\\ e^{\frac{j\pi k_1}{4}}{v}_m\\ e^{\frac{j\pi \left(2n+k_2\right)}{4}}{v}_m\end{array}\right]\mathrm{and}$$W_{m,m^{\prime },n,k_1,k_2}^{\left(2\right)}=\frac{1}{\sqrt{32}}\left[\begin{array}{cc}{v}_m& v_{m^{\prime }}\\ e^{\frac{j\pi n}{2}}{v}_m& -e^{\frac{j\pi n}{2}}{v}_{m^{\prime }}\\ e^{\frac{j\pi k_1}{4}}{v}_m& e^{\frac{j\pi k_1}{4}}{v}_{m^{\prime }}\\ e^{\frac{j\pi \left(2n+k_2\right)}{4}}{v}_m& -e^{\frac{j\pi \left(2n+k_2\right)}{4}}{v}_{m^{\prime }}\end{array}\right].$

(240) In another method, the configuration for two vertical beams allows them to be either identical or adjacent. For example, for both l=1,2 with either u.sub.k.sub.1=e.sup.jπk.sup.1.sup./2 or e.sup.jπk.sup.1.sup./4, (k.sub.1,k.sub.2) values are jointly selected from TABLE 5. Note that compared to the previous two methods where 4-bit indication is needed (k.sub.1,k.sub.2) feedback, a 3-bit indication is needed in this method.

(241) TABLE-US-00013 TABLE 5 Two vertical beam index table Index (k.sub.1, k.sub.2) 0 (0, 0) 1 (1, 1) 2 (2, 2) 3 (3, 3) 4 (0, 1) 5 (1, 2) 6 (2, 3) 7 (3, 0)

(242) In another method, when N.sub.2=4 and we have a double vertical codebook with oversampling factor o.sub.2=4 and four beams in a group represented by the first stage vertical codebook (L.sub.2=4), then (k.sub.1,k.sub.2) is derived based on TABLE 6, which is similar to indices m and m′ in rank 2 8-Tx codebook (TABLE 4). Note that here (k.sub.1,k.sub.2) corresponds to indices of two 4-Tx DFT beams from the first stage vertical codebook.

(243) TABLE-US-00014 TABLE 6 Two vertical beam index TABLE for double vertical codebook i.sub.3 i.sub.4 (k.sub.1, k.sub.2) 0-15 0 2i.sub.1, 2i.sub.1 1 2i.sub.1 + 1, 2i.sub.1 + 1 2 2i.sub.1 + 2, 2i.sub.1 + 2 3 2i.sub.1 + 3, 2i.sub.1 + 3 4    2i.sub.1, 2i.sub.1 + 1 5 2i.sub.1 + 1, 2i.sub.1 + 2 6    2i.sub.1, 2i.sub.1 + 3 7 2i.sub.1 + 1, 2i.sub.1 + 3

(244) Note that the two vertical beam idea is general and hence is applicable to other antenna port configurations such as the ones shown in FIG. 12 and FIG. 13.

(245) PMI Feedback Indices: WB V-PMI

(246) A UE can be configured to report three PMI indices, i.sub.1, i.sub.2, and i.sub.3, for informing eNB of m, m′, n, k, used for constructing a precoder according to a codebook construction associated with FIG. 11 or FIG. 12 or FIG. 13. In one method, i.sub.1, i.sub.2 correspond to precoders W.sub.m,n,k.sup.(1) and W.sub.m,m′,n.sup.(2) according to the relation in TABLE 3 and TABLE 4 respectively for the cases of RI=1 and RI=2; and i.sub.3 is mapped to k according to relation of k=i.sub.3.

(247) As k=i.sub.3 is essentially a vertical beam index, which may not change quickly over time and frequency. Hence, it is proposed to jointly feedback i.sub.1 and i.sub.3 in PUCCH feedback modes.

(248) FIG. 18 illustrates PUCCH mode 1-1 submode 1 according to embodiments of the present disclosure. The embodiment shown in FIG. 18 is for illustration only. Other embodiments could be used without departing from the scope of the present disclosure.

(249) In the embodiment, a UE is configured with PUCCH feedback mode 1-1 submode 1. Then, the UE reports RI, i.sub.1 and i.sub.3 in RI reporting instances, and the UE reports i.sub.2 and corresponding CQI in PMI/CQI reporting instances. This is illustrated in FIG. 18, where i.sub.1, i.sub.2 and i.sub.3 are denoted as W1, W2 and W3.

(250) For the joint encoding of RI, i.sub.1 and i.sub.3, two methods are designed in TABLE 7 and TABLE 8. In one method illustrated in TABLE 7, the numbers of states for RI=1 and RI=2 case are both 8, the same as Rel-10 8-Tx codebook. To jointly encode i.sub.1 and i.sub.3, it is proposed to uniformly subsample i.sub.1 with sampling factor 4, and uniformly subsample i.sub.3 with subsampling factor 2. In this case, the joint coding index 0, 1, . . . and 7 for RI/PMI 1/PMI 3 that is for RI=1, would correspond to (i.sub.1, i.sub.3)=(0, 0), (0, 1), (4, 0), (4, 1), (8, 0), (8, 1), (12, 0) and (12, 1).

(251) TABLE-US-00015 TABLE 7 Joint encoding of RI, i.sub.1 and i.sub.3 for PUCCH mode 1-1 submode 1  Value of joint encoding of RI and the first and  the third PMI Codebook index  RI/PMI 1/PMI 3 RI Codebook index i.sub.1 i.sub.3  0-7 1 $4.Math.\frac{I_{RI/\mathrm{PMI}1/\mathrm{PMI}3}}{2}.Math.$ I.sub.RI/PMI 1/PMI 3 mod 2   8-15 2 $4.Math.\frac{\left(I_{\mathrm{RI}/\mathrm{PMI}1/\mathrm{PMI}3}-8\right)}{2}.Math.$ I.sub.RI/PMI 1/PMI 3 mod 2

(252) In another method illustrated in TABLE 8, the numbers of states for RI=1 and RI=2 case are both 16, double the corresponding number of states in Rel-10 8-Tx codebook. To jointly encode i.sub.4 and i.sub.3, it is proposed to uniformly subsample i.sub.1 with sampling factor 4, but not to subsample i.sub.3, in order to maintain the elevation beamforming gain. In this case, the joint coding index 0, 1, . . . and 15 for RI/PMI 1/PMI 3 that is for RI=1, would correspond to (i.sub.1, i.sub.3)=(0, 0), (0, 1), (0, 2), (0, 3), (4, 0), (4, 1), (4, 2), (4, 3), (8, 0), (8, 1), (8, 2), (8, 3), (12, 0), (12, 1), (12, 2) and (12, 3).

(253) TABLE-US-00016 TABLE 8 Joint encoding of RI, i.sub.1 and i.sub.3 for PUCCH mode 1-1 submode 1 Value of joint encoding of RI and the first and the third PMI Codebook index RI/PMI 1/PMI 3 RI Codebook index i.sub.1 i.sub.3  0-15 1 0$4.Math.\frac{I_{RI/\mathrm{PMI}1/\mathrm{PMI}3}}{4}.Math.$ I.sub.RI/PMI 1/PMI 3 mod 4 15-31 2 $4.Math.\frac{\left(I_{\mathrm{RI}/\mathrm{PMI}1/\mathrm{PMI}3}-16\right)}{4}.Math.$ I.sub.RI/PMI 1/PMI 3 mod 4

(254) FIG. 19 illustrates an UE elevation angle distribution in cellular wireless systems, in urban macro (UMa) and urban micro (UMi) cases. The elevation angle (θ) is defined in such a way that to the zenith is zero degree, and to the horizon is 90 degrees. In most cases, base station serves UEs below the base station antennas, in which case the elevation angle is 90 degrees or larger. This intuition is verified by simulation results, as shown on the right side of FIG. 19. As for V.sub.k.sup.(1) precoders, [1 1] and [1 j] are most frequently chosen, each of which respectively corresponds to an elevation angle of 90 degrees and an angle between 90 degrees and 180 degrees. In some embodiments, the V.sub.k.sup.(1) codebook comprises two precoders:

(255) $\left\{\frac{1}{\sqrt{2}}\left[\begin{array}{c}1\\ 1\end{array}\right],\frac{1}{\sqrt{2}}\left[\begin{array}{c}1\\ j\end{array}\right]\right\},$
so that UE can recommend one of the two elevation steering angles of θ=90° and 90°<θ<180°.

(256) In some embodiments, V.sub.k.sup.(1) codebook comprises four precoders as in other embodiments of the current disclosure, and a UE can report a codebook index out of k=0, 1, 2, 3 when the PMI is reported on PUSCH. When the PMI is reported on PUCCH and when a certain feedback mode is configured, a UE reports a codebook index out of a subsampled set.

(257) In one method, the subsampled set corresponds to

(258) $\left\{\frac{1}{\sqrt{2}}\left[\begin{array}{c}1\\ 1\end{array}\right],\frac{1}{\sqrt{2}}\left[\begin{array}{c}1\\ j\end{array}\right]\right\},$
so that UE can recommend one of the two elevation steering angles of θ=90° and 90°<θ<180°.

(259) In another method, the subsampled set corresponds to

(260) $\left\{\frac{1}{\sqrt{2}}\left[\begin{array}{c}1\\ 1\end{array}\right],\frac{1}{\sqrt{2}}\left[\begin{array}{c}1\\ -1\end{array}\right]\right\},$
so that UE can recommend one of the two precoders separated farthest in the angular domain. This method can improve MU-MIMO throughput, when eNB receives PMI constructed according to this method and applies the recommended precoders in the MU-MIMO transmissions.

(261) In another method, the subsampled set is higher-layer configured, e.g., between

(262) $\left\{\frac{1}{\sqrt{2}}\left[\begin{array}{c}1\\ 1\end{array}\right],\frac{1}{\sqrt{2}}\left[\begin{array}{c}1\\ j\end{array}\right]\right\}\mathrm{and}\left\{\frac{1}{\sqrt{2}}\left[\begin{array}{c}1\\ 1\end{array}\right],\frac{1}{\sqrt{2}}\left[\begin{array}{c}1\\ -1\end{array}\right]\right\},$

(263) PMI Feedback Indices: SB V-PMI

(264) A UE can be configured to report three PMI indices, i.sub.1, i.sub.2, and i.sub.3, for informing eNB of m, m′, n, k, used for constructing a precoder according to a codebook construction associated with FIG. 13 or FIG. 14 or FIG. 15. In one method, i.sub.1, i.sub.2 correspond to precoders W.sub.m,n,k.sup.(1) and W.sub.m,m′,n.sup.(2) according to the relation in TABLE 3 and TABLE 4 respectively for the cases of RI=1 and RI=2; and i.sub.3 is mapped to k according to relation of k=i.sub.3.

(265) To adapt to the fast variation in the vertical channel directions, the vertical beam index k=i.sub.3 may need to reported per SB. It is therefore proposed to jointly feedback i.sub.2 and i.sub.3 in PUCCH feedback modes.

(266) FIGS. 20 to 22 illustrate three examples of PUCCH mode 1-1 submode 1 2000, 2100, and 2200 according to embodiments of the present disclosure. The embodiments shown in FIGS. 20 to 22 are for illustration only. Other embodiments could be used without departing from the scope of the present disclosure.

(267) In the embodiments, a UE is configured with PUCCH feedback mode 1-1 submode 1. Then, the UE reports RI and i.sub.1 in RI reporting instances, and the UE reports i.sub.2, i.sub.3, and corresponding CQI in PMI/CQI reporting instances. This is illustrated in FIG. 20, where i.sub.1, i.sub.2 and i.sub.3 are denoted as W1, W2 and W3.

(268) PMI Feedback Indices: Double Structure

(269) A UE can be configured to report four PMI indices, i.sub.1,1, i.sub.2,1, i.sub.1,2, and i.sub.2,2 corresponding to codebooks W.sub.1.sup.(1), W.sub.2.sup.(1), W.sub.1.sup.(2), and W.sub.2.sup.(2), respectively according to some embodiments of this disclosure. The eNB uses them for constructing a precoder according to a codebook construction associated with FIG. 13 or FIG. 14 or FIG. 15, where index k is derived from i.sub.1,2 and i.sub.2,2. In one method, i.sub.1,1, i.sub.2,1 correspond to precoders W.sub.m,m,k.sup.(1) and W.sub.m,m′,n.sup.(2) according to the relation in TABLE 3 and TABLE 4 respectively for the cases of RI=1 and RI=2; and i.sub.1,2 and i.sub.2,2 are mapped to k according to relation of k=s.sub.2i.sub.1,2+i.sub.2,2, wherein s.sub.2 (e.g., s.sub.2=2) is a skipping number for the second dimension, and i.sub.2,2=0, 1, . . . , L.sub.2−1.

(270) According to the double codebook structure, it is proposed to jointly feedback (i.sub.1, i.sub.3) and (i.sub.2, i.sub.4) in PUCCH feedback modes.

(271) In one embodiment, a UE is configured with PUCCH feedback mode 1-1 submode 1. Then, the UE reports RI and (i.sub.1, i.sub.3) in RI reporting instances, and the UE reports (i.sub.2, i.sub.4), and corresponding CQI in PMI/CQI reporting instances. This is illustrated in FIG. 21, where i.sub.1, i.sub.2, i.sub.3, and i.sub.4 are denoted as W1, W2, W3 and W4.

(272) In another embodiment, a UE is configured with PUCCH feedback mode 1-1 submode 1. Then, the UE reports RI and (i.sub.1,1, i.sub.1,2) in RI reporting instances, and the UE reports (i.sub.2,1, i.sub.2,2), and i.sub.2,1 alternatively together with the corresponding CQI in PMI/CQI reporting instances. Note that in this mode, if the number of feedback bits in PMI/CQI reporting instances is fixed, then the UE can report a course and a fine PMI feedback for W2: W2 reported together with W4 is a course feedback and W2 reported alone is a refined feedback. This is illustrated in FIG. 22, where i.sub.1,1, i.sub.2,1, i.sub.1,2, and i.sub.2,2 are denoted as W1, W2, W3 and W4.

(273) In one example, i.sub.2,1 indicates one out of 4 horizontal beams and i.sub.2,2 indicates one out of 2 vertical beams (for example Scheme 2 in).

(274) In some embodiments, total number of feedback bits in PMI/CQI reporting instances is 4, of which 2 bits are used for co-phase selection and the remaining two bits are used for selecting a composite beam, constructed by Kronecker product of a horizontal beam vector and a vertical beam vector.

(275) In PMI/CQI reporting instances in which W2+CQI are reported, these remaining 2 bits are used to indicate one horizontal beam out of the 4 horizontal beams. This is referred to as a fine PMI because all 4 beams are considered in the PMI selection.

(276) On the other hand, in PMI/CQI reporting instances in which W2+W4+CQI are reported, 1 bit is used to select one vertical beam out of 2 beams and 1 bit is used to select a horizontal PMI from a subsampled set of 4 horizontal beams. This is referred to as a coarse PMI because a subset of 4 beams are considered in the PMI selection. In one method (Method 1), the subsampled set corresponds to beam indices {1,2} out of four horizontal beam indices {1,2,3,4} indicated by i.sub.1. In another method (Method 2), the subsampled set corresponds to beam indices {1,3} out of four horizontal beam indices {1,2,3,4} indicated by i.sub.1

(277) A subsampling method may be indicated according to TABLE 9. In one method, eNB may configure the UE a subsampling method for deriving i.sub.2. In another method, the UE may feedback a selected subsampling method using a 1-bit filed. Such feedback may be WB and long-term.

(278) TABLE-US-00017 TABLE 9 Horizontal beam index subsample method Method Subsampled horizontal beam index set 1 {1, 2} 2 {1, 3}

(279) In another embodiment, a UE is configured with PUCCH feedback mode 1-1 submode x, as shown in FIG. 23, for reporting i.sub.1,1, i.sub.2,1, i.sub.1,2, and i.sub.2,2 using two CSI processes: CSI processes 1 and 2. According to CSI processes 1, the UE reports RI and i.sub.1,1 in RI reporting instances, and it reports i.sub.2,1 and the corresponding CQI in PMI/CQI reporting instances. Similarly, according to CSI processes 2, the UE reports RI and i.sub.1,2 in RI reporting instances, and it reports i.sub.2,2 and the corresponding CQI in PMI/CQI reporting instances.

(280) In one method, the two RIs and CQIs in the CSI reports correspond to the joint RI and joint CQI. In another method, one of them, for example CSI report 1 includes joint RI and joint CQI, and the other report includes V-RI and V-CQI, for example. In yet another method, both or one of RI and CQI are reported only once in one of the CSI reports.

(281) The parametrized KP double codebook described above is summarized as follows.

(282) In some embodiments, a UE is configured with a CSI-RS configuration via higher layer, configuring Q antenna ports—antenna ports A(1) 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.sub.1 and N.sub.2, which respectively indicates a first number or quantity 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.Math.N.sub.1.Math.N.sub.2.

(283) In some embodiments of the disclosure, 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.sub.1,N.sub.2)=(N,M).

(284) In some embodiments of the disclosure, 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.sub.1,N.sub.2)=(M,N).

(285) In various embodiments, downlink signaling may indicate first and second quantities of antenna ports. These first and second quantities of antenna ports indicate respective quantities of antenna ports in first and second dimensions. For example, the first quantity of antenna ports is a number or value for antenna ports in a first dimension. For example, the first dimension may be a vertical direction or rows or may be the horizontal direction or columns. In another example, the second quantity of antenna ports is a number or value for antenna ports in a second dimension. For example, the second dimension may be a vertical direction or rows or may be the horizontal direction or columns. Also, the first and second quantities of subset beams indicates respective quantities of subset beams in first and second dimensions. For example, the first quantity of subset beams is a number or value for subset beams in a first dimension.

(286) In the rest of the disclosure, we will use notation (N.sub.1,N.sub.2) in place of (M,N) or (N,M). Similarly, we will use (O.sub.1,O.sub.2) for the oversampling factors in the two dimensions in place of (S.sub.N, S.sub.M) or (S.sub.M, S.sub.N).

(287) In one embodiment, for each of [8], 12 and 16 Tx ports, a precoding matrix W in the codebook is represented as:
W=W.sub.1W.sub.2
where:

(288) $W_1=\left(\begin{array}{cc}{X}_1.Math.X_2& 0\\ 0& X_1.Math.X_2\end{array}\right),$
W.sub.2 FFS; X.sub.1 is a Ar.sub.1×L.sub.1 matrix with L.sub.1 column vectors being an O.sub.1x oversampled DFT vector of length N.sub.1:

(289) $v_l={\left[\begin{array}{cccc}1& e^{\frac{j2\pi l}{N_1{O}_1}}& \mathrm{.Math.}& e^{\frac{j2\pi \left(N_1-1\right)l}{N_1{O}_1}}\end{array}\right]}^t;$ X.sub.2 is a N.sub.2×L.sub.2 matrix with L.sub.2 column vectors being an O.sub.2x oversampled DFT vector of length N.sub.2:

(290) $v_l={\left[\begin{array}{cccc}1& e^{\frac{j2\pi l}{N_2{O}_2}}& \mathrm{.Math.}& e^{\frac{j2\pi \left(N_2-1\right)l}{N_2{O}_2}}\end{array}\right]}^t;$ N.sub.1 and N.sub.2 are the numbers of antenna ports per pol in 1.sup.st and 2.sup.nd dimensions; FFS whether to select different beams (e.g. different X1 or X2) for the two pols; FFS column selection from KP applied to W.sub.1.

(291) A first alternative to construct such a codebook is as follows. Tall, [square] and wide arrays are supported with a single codebook for each of [8], 12 and 16 CSI-RS ports: For PUSCH and PUCCH reporting, a codebook subset can be separately selected via RRC signaling of codebook subset selection parameters or a bitmap; FFS beam subset selection/restriction and related mechanism; and FFS which and how the parameters (in TABLE 1) are related/configured.

(292) A second alternative to construct such a codebook is as follows. Tall, square and wide port layouts are supported with parameters N.sub.1, N.sub.2: Values of N.sub.1 and N.sub.2 are RRC signaled. The parameters (in TABLE 10) define the codebook: Configurable oversampling factors, RRC signaled, values FFS; Other parameters are to be determined; FFS beam subset selection/restriction and related mechanism.

(293) TABLE-US-00018 TABLE 10 1: Codebook parameters Parameter per dimension Remark Oversampling factors O.sub.d Determines total number of beams Q.sub.d = O.sub.d .Math. N.sub.d, d = 1, 2 in the codebook. Beam group spacing Difference of the leading beam indices of two adjacent beam groups Number of beams in each beam May depend on rank and/or W1 group Beam spacing Difference of two adjacent beam indices in each beam group

(294) A beam grouping scheme and a codebook can be defined in terms of two groups of parameters, one group per dimension. A group of parameters for dimension d comprises at least one of the following parameters: a number of antenna ports per pol N.sub.d.sup..Math.; an oversampling factor O.sub.d.sup..Math.; a skip number (or beam group spacing) s.sub.d (for W1); a beam offset number f.sub.d; a beam spacing number p.sub.d (for W2); and a number of beams (in each beam group) L.sub.d.

(295) A beam group indicated by a first PMI i.sub.1,d of dimension d (corresponding to W.sub.d.sup.(1)), is determined based upon these six parameters. The total number of beams is N.sub.d.Math.O.sub.d; and the beams are indexed by an integer m.sub.d, wherein beam m.sub.d, v.sub.m.sub.d, corresponds to a precoding vector

(296) $v_{m_d}={\left[\begin{array}{cccc}1& e^{j\frac{2\pi m_d}{O_d{N}_d}}& \mathrm{.Math.}& e^{j\frac{2\pi m_d\left(N_d-1\right)}{O_d{N}_d}}\end{array}\right]}^t,$
m.sub.d=0, . . . , N.sub.d.Math.O.sub.d−1. The first PMI of the first dimension i.sub.1,d, i.sub.1,d=0, . . . , N.sub.d.Math.O.sub.d/s.sub.d−1, can indicate any of L.sub.d beams indexed by: m.sub.d=f.sub.d+s.sub.d.Math.i.sub.1,d,f.sub.d+s.sub.d.Math.i.sub.1,d+p.sub.d, . . . , f.sub.d+s.sub.d.Math.i.sub.1,d+(L.sub.d−1) p.sub.d, where these L.sub.d beams are referred to as a beam group.

(297) In one example, N.sub.1=4 and N.sub.2=4. Three illustrative beam grouping schemes, referred to as Scheme 1, Scheme 2, and Scheme 3, according to the double codebook structure are shown in FIG. 4, FIG. 5 and FIG. 6, and the parameters are listed in TABLE 11.

(298) TABLE-US-00019 TABLE 11 Parameters for three example beam grouping schemes A 1st A 1st A 1st A 2nd A 2.sup.nd A 2.sup.nd over-sampling beam number of overs-ampling beam number of factor O.sub.1 for spacing p.sub.1 beams L.sub.1 factor O.sub.2 for spacing p.sub.2 beams L.sub.2 the 1st for the 1st for the 1.sup.st the 2nd for the 2.sup.nd for the 2.sup.nd dimension dimension dimension dimension dimension dimension Scheme 1 8 1 4 4 1 1 Scheme 2 8 1 1 4 1 4 Scheme 3 8 1 2 4 1 2

(299) FIGS. 24 to 26 illustrates respective beam grouping schemes 1, 2 and 3 according to embodiments of the present disclosure. The embodiments shown in FIGS. 24 to 26 are for illustration only. Other embodiments could be used without departing from the scope of the present disclosure.

(300) In some embodiments, the scheme is determined according to antenna (port) dimension parameters (N.sub.1, N.sub.2), where N.sub.1 and N.sub.1 are configured by the higher layer (RRC). In one example, if a UE is configured with (N.sub.1, N.sub.2)=(8,1), scheme 1 is configured; if the UE is configured (4,2), on the other hand, scheme 2 is configured.

(301) In these schemes, a horizontal oversampling factor O.sub.1=8 is considered for W.sub.1.sup.(1) codebook and a vertical oversampling factor O.sub.2=4 is considered for W.sub.2.sup.(1) codebook. Hence, total number of beams for W.sub.1.sup.(1) codebook is N.sub.1O.sub.1=32, and total number of beams for W.sub.2.sup.(1) codebook is N.sub.2O.sub.2=16. FIGS. 24 to 26 illustrate these 16×32 3D beams constructed by Kronecker product of each beam vector in W.sub.1.sup.(1) codebook and each beam vector in W.sub.2.sup.(1) codebook as a 16×32 grid, wherein each square correspond to a beam.

(302) The focus of this disclosure is on the details of configuring KP codebook based on the codebook parameters: (N.sub.d, O.sub.d, s.sub.d, f.sub.d, p.sub.d, L.sub.d) where d=1,2.

(303) In some embodiments: the UE is configured with a parameterized KP codebook corresponding to the codebook parameters (N.sub.d, O.sub.d, s.sub.d, f.sub.d, p.sub.d, L.sub.d) where d=1,2 from a master codebook by applying codebook subset selection. The master codebook is a large codebook with default codebook parameters.

(304) In one method, the master codebook may be unique. In another method, there may be multiple master codebooks and the UE may be configured with at least one master codebook from the multiple master codebooks. An example of multiple master codebooks may be based on beam offset numbers f.sub.1 and f.sub.2 as shown in the table below. In this example, a 1-bit indication may be used to indicate the master codebook via higher layer such as RRC.

(305) TABLE-US-00020 TABLE 12 f.sub.1 f.sub.2 Master codebook 0 0 0 Master codebook 1 0, 1, . . . , s.sub.1 − 1 0, 1, . . . , s.sub.2 − 1

(306) For simplicity, it is assumed that f.sub.1=f.sub.1=0 (Mater codebook 0) in the rest of the disclosure. However, the disclosure is applicable to other values of f.sub.1 and f.sub.2.

(307) An example of master codebook parameters for Q=8, 12, 16, and 32 antenna ports (L.sub.1,L.sub.2)=(4,4) are tabulated in TABLE 3. It is noted that Q=MNP in TABLE 13.

(308) TABLE-US-00021 TABLE 13 Master codebook parameters for Q = 12, 16, and 32 antenna ports and (L.sub.1, L.sub.2) = (4, 4) Q N.sub.1 N.sub.2 P O.sub.1 O.sub.2 L.sub.1 L.sub.2 p.sub.1 p.sub.2 s.sub.1 s.sub.2 8 4 1 2 8 1 4 1 1 1 1 1, 2, 4 8 2 2 2 2, 4, 8 2, 4, 8 4 4 1, 2 1, 2 1, 2, 4 1, 2, 4 12 3 2 2 2, 4, 8 2, 4, 8 4 4 1, 2 1, 2 1, 2, 4 1, 2, 4 12 2 3 2 2, 4, 8 2, 4, 8 4 4 1, 2 1, 2 1, 2, 4 1, 2, 4 16 4 2 2 2, 4, 8 2, 4, 8 4 4 1, 2 1, 2 1, 2, 4 1, 2, 4 16 2 4 2 2, 4, 8 2, 4, 8 4 4 1, 2 1, 2 1, 2, 4 1, 2, 4 32 4 4 2 2, 4, 8 2, 4, 8 4 4 1, 2 1, 2 1, 2, 4 1, 2, 4 32 8 2 2 2, 4, 8 2, 4, 8 4 4 1, 2 1, 2 1, 2, 4 1, 2, 4

(309) In some embodiments, the beam grouping and beam skipping parameters (s.sub.1, s.sub.2, p.sub.1, and p.sub.2) of the master codebook are fixed and hence are not configured. For example, they are fixed to s.sub.1=s.sub.2=2, and p.sub.1=p.sub.2=1.

(310) In some embodiments, the master codebook parameters for Q=8, 12, 16, and 32 antenna ports and (L.sub.1,L.sub.2)=(4,2) are according to TABLE 14, where multiple oversampling factors in two dimension are supported. The remaining codebook parameters may be fixed, for example, s.sub.1=s.sub.2=2, and p.sub.1=p.sub.2=1.

(311) TABLE-US-00022 TABLE 14 Master codebook parameters for Q = 12, 16, and 32 antenna ports and (L.sub.1, L.sub.2) = (4, 2) Q N.sub.1 N.sub.2 P O.sub.1 O.sub.2 L.sub.1 L.sub.2 8 2 2 2 2, 4, 8 2, 4, 8 4 2 12 3 2 2 2, 4, 8 2, 4, 8 4 2 12 2 3 2 2, 4, 8 2, 4, 8 4 2 16 4 2 2 2, 4, 8 2, 4, 8 4 2 16 2 4 2 2, 4, 8 2, 4, 8 4 2 32 4 4 2 2, 4, 8 2, 4, 8 4 2 32 8 2 2 2, 4, 8 2, 4, 8 4 2

(312) The oversampling factor in one or both dimensions is configurable according to the below table.

(313) TABLE-US-00023 Oversampling factor O.sub.d in dimension d where d = 1, 2 2, 4, 8

(314) In some embodiments, the master codebook parameters for Q=8, 12, 16, and 32 antenna ports and (L.sub.1,L.sub.2)=(4,2) are according to TABLE 15, where single oversampling factors in two dimension are supported. The remaining codebook parameters may be fixed, for example, s.sub.1=s.sub.2=2, and p.sub.1=p.sub.2=1.

(315) TABLE-US-00024 TABLE 15 Master codebook parameters for Q = 12, 16, and 32 antenna ports and (L.sub.1, L.sub.2) = (4, 2) Q N.sub.1 N.sub.2 P O.sub.1 O.sub.2 L.sub.1 L.sub.2 8 2 2 2 8 8 4 2 12 3 2 2 8 8 4 2 12 2 3 2 8 8 4 2 16 4 2 2 8 8 4 2 16 2 4 2 8 8 4 2 32 4 4 2 8 8 4 2 32 8 2 2 8 8 4 2

(316) In some embodiments, the UE may be configured with one of multiple beam grouping schemes or (L.sub.1,L.sub.2) value. Depending on the configured (L.sub.1,L.sub.2), the other codebook parameters such as beam skipping parameters (s.sub.1,s.sub.2) are determined by the UE. For example, when the UE is configured with (L.sub.1,L.sub.2)=(4,2), then UE determines s.sub.1=s.sub.2=2, and when the UE is configured with (L.sub.1,L.sub.2)=(1,1), then UE determines s.sub.1=s.sub.2=1. The number of W1 bits for the former, i.e., (L.sub.1,L.sub.2)=(4,2), is log 2(O.sub.1N.sub.1/2)+log 2(O.sub.2N.sub.2/2), whereas it is log 2(O.sub.1N.sub.1)+log 2(O.sub.2N.sub.2) for the later (i.e., (L.sub.1,L.sub.2)=(1,1)), which is correspond to 2 more bits than the former.

(317) FIG. 27 illustrates a master codebook 2700 with example beam groups for N.sub.1=4 and N.sub.2=4 according to embodiments of the present disclosure. The embodiment shown in FIG. 27 is for illustration only. Other embodiments could be used without departing from the scope of the present disclosure.

(318) An example of the master codebook is a fine DFT codebook that is obtained by performing the KP of azimuth (1.sup.st dimension) and elevation (2.sup.nd dimension) DFT codebooks with large oversampling factors. For example, as shown in the figure, the oversampling factor may be 8 in azimuth dimension, i.e., O.sub.1=8 and it may be 4 in elevation dimension, i.e., O.sub.2=4. An example of the master codebook for N.sub.1=4 azimuth antenna ports and N.sub.2=4 elevation antenna ports is shown in FIG. 27. As shown, there are N.sub.1O.sub.1=32 azimuth DFT beams indexed by h=0,1,2, . . . , 31 and N.sub.2O.sub.2=16 elevation DFT beams indexed by v=0,1,2, . . . , 15. So, the total number of 2D DFT beams that are obtained by the KP of the azimuth and elevation DFT codebooks is 32×16=512.

(319) From this 2D grid of DFT beams, beam groups of a default size are formed. An example of default size of beam groups is (L.sub.1, L.sub.2)=(4, 4) as in FIG. 27. The beam groups are formed based on all possible values of s.sub.1 and s.sub.2. The set of all beam groups constitutes the master W1 codebook. A few example beam group for s.sub.1=1 and s.sub.2=1 are shown in FIG. 27 7 as shaded squares.

(320) From these beam groups of default size, the beam selection and co-phasing are performed to construct pre-coding matrices corresponding to different number of layers v=1, 2, 3 . . . 8. For example, for v=1, one beam is selected from the 16 beams in a beam group and a co-phasing φ is applied from the QPSK co-phasing codebook={1,j,−1,−j} to form a pre-coding vector (as shown in FIG. 27 for beam a.sub.0,0). The set of pre-coding matrices that are constructed in this manner constitute the master W2 codebook.

(321) In some embodiments, the master codebook is represented as a set of master sub-codebooks where each master sub-codebook corresponds to a unique set of codebook parameters (N.sub.d, o.sub.d, s.sub.d, p.sub.d) where d=1,2. For example, for the master codebooks in TABLE 13, the master sub-codebooks may map to the codebook parameters according to the following TABLE 16. For simplicity, in the table, parameters (N.sub.d, o.sub.d) where d=1,2, are not shown since they take single values according to TABLE 13.

(322) TABLE-US-00025 TABLE 16 Sub-codebook to codebook parameter mapping Sub-codebook Index p.sub.1 (for W2) p.sub.2 (for W2) s.sub.1 (for W1) s.sub.2 (for W1) 0 1 1 1 1 1 1 2 2 1 4 3 2 1 4 2 2 5 2 4 6 4 1 7 4 2 8 4 4 9 1 2 1 1 . . . . . . . . . 17  4 4 18  2 1 1 1 . . . . . . . . . 26  4 4 27  2 2 1 1 . . . . . . . . . 35  4 4

(323) In some embodiments, TABLE 17 is used as a rank-1 (1 layer) master codebook that can be used for any of Q=12, 16 and 32 antenna configurations, wherein the corresponding rank 1 precoder is

(324) 0$W_{m_1,m_2,n}^{\left(1\right)}=\frac{1}{\sqrt{Q}}\left[\begin{array}{c}{v}_{m_1}.Math.u_{m_2}\\ {\phi }_n{v}_{m_1}.Math.u_{m_2}\end{array}\right].$
In this table, the 2.sup.nd dimension beam index m.sub.2 increases first as i.sub.2 increases.

(325) TABLE-US-00026 TABLE 17 Master codebook for 1 layer CSI reporting for L.sub.1 = L.sub.2 = 4 i.sub.2 0 1 2 3 Precoder W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.,0.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.,1.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.,2.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.,3.sup.(1) i.sub.2 4 5 6 7 Precoder W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.+p.sub.2.sub.,0.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.+p.sub.2.sub.,1.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.+p.sub.2.sub.,2.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.+p.sub.2.sub.,3.sup.(1) i.sub.2 8 9 10 11 Precoder W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.+2p.sub.2.sub.,0.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.+2p.sub.2.sub.,1.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.+2p.sub.2.sub.,2.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.+2p.sub.2.sub.,3.sup.(1) i.sub.2 12 13 14 15 Precoder W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.+3p.sub.2.sub.,0.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.+3p.sub.2.sub.,1.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.+3p.sub.2.sub.,2.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.+3p.sub.2.sub.,3.sup.(1) i.sub.2 16-31 Precoder Entries 16-31 constructed with replacing the second subscript s.sub.1i.sub.1,1 with s.sub.1i.sub.1,1 + p.sub.1 in entries 0-15. i.sub.2 32-47 Precoder Entries 32-47 constructed with replacing the second subscript s.sub.1i.sub.1,1 with s.sub.1i.sub.1,1 + 2p.sub.1 in entries 0-15. i.sub.2 48-63 Precoder Entries 48-63 constructed with replacing the second subscript s.sub.1i.sub.1,1 with s.sub.1i.sub.1,1 + 3p.sub.1 in entries 0-15.

(326) In some embodiments, TABLE 18 is used as a rank-1 (1 layer) master codebook that can be used for any of Q=12, 16 and 32 antenna configurations, wherein the corresponding rank 1 precoder is

(327) $W_{m_1,m_2,n}^{\left(1\right)}=\frac{1}{\sqrt{Q}}\left[\begin{array}{c}{v}_{m_1}.Math.u_{m_2}\\ {\phi }_n{v}_{m_1}.Math.u_{m_2}\end{array}\right].$
In this table, the 1.sup.st dimension beam index m.sub.1 increases first as i.sub.2 increases.

(328) TABLE-US-00027 TABLE 18 Master codebook for 1 layer CSI reporting for L.sub.1 = L.sub.2 = 4 i.sub.2 0 1 2 3 Precoder W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.,0.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.,1.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.,2.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.,3.sup.(1) i.sub.2 4 5 6 7 Precoder W.sub.s.sub.1.sub.i.sub.1,1.sub.+p.sub.1.sub.,s.sub.2.sub.i.sub.1,2.sub.,0.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.+p.sub.1.sub.,s.sub.2.sub.i.sub.1,2.sub.,1.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.+p.sub.1.sub.,s.sub.2.sub.i.sub.1,2.sub.,2.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.+p.sub.1.sub.,s.sub.2.sub.i.sub.1,2.sub.,3.sup.(1) i.sub.2 8 9 10 11 Precoder W.sub.s.sub.1.sub.i.sub.1,1.sub.+2p.sub.1.sub.,s.sub.2.sub.i.sub.1,2.sub.,0.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.+2p.sub.1.sub.,s.sub.2.sub.i.sub.1,2.sub.,1.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.+2p.sub.1.sub.,s.sub.2.sub.i.sub.1,2.sub.,2.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.+2p.sub.1.sub.,s.sub.2.sub.i.sub.1,2.sub.,3.sup.(1) i.sub.2 12 13 14 15 Precoder W.sub.s.sub.1.sub.i.sub.1,1.sub.+3p.sub.1.sub.,s.sub.2.sub.i.sub.1,2.sub.,0.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.+3p.sub.1.sub.,s.sub.2.sub.i.sub.1,2.sub.,1.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.+3p.sub.1.sub.,s.sub.2.sub.i.sub.1,2.sub.,2.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.+3p.sub.1.sub.,s.sub.2.sub.i.sub.1,2.sub.,3.sup.(1) i.sub.2 16-31 Precoder Entries 16-31 constructed with replacing the second subscript s.sub.2i.sub.1,2 with s.sub.2i.sub.1,2 + p.sub.2 in entries 0-15. i.sub.2 32-47 Precoder Entries 32-47 constructed with replacing the second subscript s.sub.2i.sub.1,2 with s.sub.2i.sub.1,2 + 2p.sub.2 in entries 0-15. i.sub.2 48-63 Precoder Entries 48-63 constructed with replacing the second subscript s.sub.2i.sub.1,2 with s.sub.2i.sub.1,2 + 3p.sub.2 in entries 0-15.

(329) In some embodiments, the UE reports i.sub.2,1, i.sub.2,2 and n in place of i.sub.2, in which case m.sub.1 and m.sub.2 are determined as: m.sub.1=s.sub.1i.sub.1,1+i.sub.2,1 and m.sub.1=s.sub.2i.sub.1,2+i.sub.2,2.

(330) In those embodiments related to TABLE 17 and TABLE 18, and other related embodiments, the parameters s.sub.1, s.sub.2, p.sub.1, and p.sub.2 in this table can be selected, e.g., according to TABLE 13, and it is assumed that L.sub.1=L.sub.2=4. Also i.sub.1,1=0,1, . . . ,

(331) $\frac{N_1{o}_1}{{\mathrm{Ps}}_1}-1$
and i.sub.1,2=0,1, . . . ,

(332) $\frac{N_2{o}_2}{s_2}-1.$

(333) The master codebook for other parameters and for more than 1 layer can be similarly constructed.

(334) Unified Codebook for Beamformed and Non-Precoded CSI-RS

(335) In some embodiments, v.sub.m.sub.1 and u.sub.m.sub.2 to comprise a precoder

(336) $W_{m_1,m_2,n}^{\left(1\right)}=\frac{1}{\sqrt{Q}}\left[\begin{array}{c}{v}_{m_1}.Math.u_{m_2}\\ {\phi }_n{v}_{m_1}.Math.u_{m_2}\end{array}\right],$
are differently configured depending on whether beamformed CSI-RS, or non-precoded CSI-RS or both are configured.

(337) In one such example with Q=16 and N.sub.1=8 and N.sub.2=2: When the UE is configured with only non-precoded CSI-RS or both types of CSI-RS, the UE is further configured to use:

(338) $\mathrm{Either}\left(\mathrm{Alt}1\right)v_{m_1}={\left[\begin{array}{cccc}1& e^{j\frac{2\pi m_1}{32}}& e^{j\frac{4\pi m_1}{32}}& e^{j\frac{6\pi m_1}{32}}\end{array}\right]}^t$$\mathrm{and}{u}_{m_2}={\left[\begin{array}{cc}1& e^{j\frac{2\pi m_2}{32}}\end{array}\right]}^t;\mathrm{or}\left(\mathrm{Alt}2\right)v_{m_1}={\left[\begin{array}{cc}1& e^{j\frac{2\pi m_2}{32}}\end{array}\right]}^t$$\mathrm{and}{u}_{m_2}={\left[\begin{array}{cccc}1& e^{j\frac{2\pi m_1}{32}}& e^{j\frac{4\pi m_1}{32}}& e^{j\frac{6\pi m_1}{32}}\end{array}\right]}^t.$ When the UE is configured with only beamformed CSI-RS, the UE is further configured to use:
v.sub.m.sub.1=e.sub.m.sub.1.sup.(4×1) and u.sub.m.sub.2=e.sub.m.sub.2.sup.(2×1)(if Alt 1 is used)
v.sub.m.sub.1=e.sub.m.sub.1.sup.(2×1) and u.sub.m.sub.2=e.sub.m.sub.2.sup.(4×1)(if Alt 2 is used) Herein e.sub.m.sup.(N×1), m=0, 1, . . . , N−1, is an N×1 column vector comprising with (N−1) elements with zero value and one element with value of one. The one element with value of one is on (m+1)-th row. For example, e.sub.1.sup.(4×1)=[0 1 0 0].sup.t; and e.sub.2.sup.(4×1)=[0 0 1 0].sup.t. In this case, the UE is further configured to use i.sub.1,1=i.sub.1,2=0 in the table entries, and the UE is configured to report only i.sub.2 as PMI, and not to report i.sub.1,1 and i.sub.1,2.

(339) The precoding vector obtained with Alt 2 can be applied on the antenna ports numbered according to FIGS. 7 and 8. In these embodiments, the first dimension corresponds to a longer dimension of the array; and the second dimension corresponds to a shorter dimension of the array. On the contrary, the precoding vector obtained with Alt 1 can be applied on the antenna ports numbered in such a way that the first dimension corresponds to a shorter dimension of the array; and the second dimension corresponds to a longer dimension of the array.

(340) In some embodiments, the UE can identify that a configured CSI-RS resource is beamformed or non-precoded by: Alt 1. Explicit RRC indication: The UE is configured with a higher-layer parameter for the configured CSI-RS resource, indicating whether the configured CSI-RS resource is beamformed or non-precoded. Alt 2. Implicit indication: The UE is configured with a different set of CSI-RS port numbers for beamformed CSI-RS than the non-precoded CSI-RS. In one example, the beamformed CSI-RS takes antenna port numbers 200-207, while the non-precoded CSI-RS takes antenna port numbers 15-30.

(341) Embodiments on Codebook Subset Restriction

(342) FIG. 28 illustrates the subset restriction on rank-1 i.sub.1,H and i.sub.1,V(or i.sub.1,1 and i.sub.1,2) for N.sub.1=8, N.sub.2=4, o.sub.1=8 and o.sub.2=4, according to embodiments of the present disclosure. The embodiment shown in FIG. 28 is for illustration only. Other embodiments could be used without departing from the scope of the present disclosure.

(343) In some embodiments, the configured values of parameters (N.sub.d, o.sub.d, s.sub.d) where d=1,2 are used to apply codebook subset restriction on of the set of i.sub.1,1 and i.sub.1,2 indices from the master codebook. An illustration of subset restriction on rank-1 i.sub.1,1 and i.sub.1,2 indices in terms of parameters s.sub.1 and s.sub.2 is shown in FIG. 28. In the figure, the shaded squares represent the rank-1 i.sub.1,1 and i.sub.1,2 indices that are obtained after subset restriction and the white squares represent the indices that are not included.

(344) In some embodiments, the codebook subset restriction on i.sub.1,1 and i.sub.1,2 indices may be applied according to a table such as TABLE 19. Depending on the values of s.sub.d where d=1,2, the subsets of i.sub.1,1 and i.sub.1,2 indices can be obtained from the table. Note that s.sub.1=s.sub.2=1 corresponds to no subset restriction. In these embodiments it is assumed that (i.sub.1,1, i.sub.1,2)=(i.sub.1,H, i.sub.1,V), but the same design can apply even if (i.sub.1,1, i.sub.1,2)=(i.sub.1,V, i.sub.1,H)

(345) TABLE-US-00028 TABLE 19 Subset restriction on rank-1 i.sub.1,H and i.sub.1,V (TABLE 17) i.sub.1,H after subset s.sub.1 restriction s.sub.2 i.sub.1,V after subset restriction 1 0, 1, 2, . . . , N.sub.1o.sub.1/P-1 1 0, 1, 2, . . . , N.sub.2o.sub.2-1 2 0, 2, 4, . . . , N.sub.1o.sub.1/P-2 2 0, 2, 4, . . . , N.sub.2o.sub.2-2 4 0, 4, 8, . . . , N.sub.1o.sub.1/P-4 4 0, 4, 8, . . . , N.sub.2o.sub.2-4

(346) An example of such a table for N.sub.1=8, N.sub.2=4, o.sub.1=8 and o.sub.2=4 is shown in TABLE 20.

(347) TABLE-US-00029 TABLE 20 Subset restriction on rank-1 i.sub.1,H and i.sub.1,V for N.sub.1 = 8, N.sub.2 = 4, o.sub.1 = 8 and o.sub.2 = 4 i.sub.1,H after subset Number of i.sub.1,V after subset Number of i.sub.1,V s.sub.1 restriction i.sub.1,H indices s.sub.2 restriction indices 1 0, 1, 2, . . . , 31 32 1 0, 1, 2, . . . , 15 16 2 0, 2, 4, . . . , 30 16 2 0, 2, 4, . . . , 14 8 4 0, 4, 8, . . . , 28 8 4 0, 4, 8, 12 4

(348) In some embodiments, the configured values of parameters (N.sub.d, o.sub.d, s.sub.d, p.sub.d, L.sub.d) where d=1,2 are used to apply codebook subset restriction on the set of rank-1 i.sub.2 indices from the master codebook. The codebook subset restriction may be applied from a table such as TABLE 21. Depending on the values of L.sub.1 and L.sub.2, the subset of rank-1 i.sub.2 indices can be obtained from a row of the table.

(349) Note that L.sub.1=L.sub.2=4 corresponds to no subset restriction. In these embodiments it is assumed that (i.sub.1,1, i.sub.1,2)=(i.sub.1,H, i.sub.1,V), but the same design can apply even if (i.sub.1,1, i.sub.1,2)=(i.sub.1,V, i.sub.1,H).

(350) TABLE-US-00030 TABLE 21 An illustration of subset restriction on rank-1 i.sub.2 (TABLE 17) Beam Corresponding grouping case i.sub.2 after subset Number of configuration (L.sub.1, L.sub.2) in FIG. 39 restriction i.sub.2 indices 0 (4, 1) 1250 0-3, 16-19, 32-35, 16 48-51 1 (1, 4) 1240 0-15 16 2 (2, 2) 1260 0-7, 16-23 16 3 (4, 2) 1230 0-7, 16-23, 32-39, 32 48-55 4 (2, 4) 1220 0-31 32 5 (4, 4) 1210 0-63 64

(351) FIG. 29 illustrates the example beam groups in the master codebook according to the present disclosure. The embodiment shown in FIG. 29 is for illustration only. Other embodiments could be used without departing from the scope of the present disclosure.

(352) The beam groups is in a size L.sub.1=L.sub.2=4 with (i.sub.1,1, i.sub.1,2)=(i.sub.1,H, i.sub.1,V)=(0,0) in the master codebook. In the FIG. 29, the four rows correspond to four different values for s.sub.1 and s.sub.2. The first column shows the corresponding 2D index map of i.sub.1,H and i.sub.1,V indices. The rest of the four columns show the beam groups with (i.sub.1,1, i.sub.1,2)=(i.sub.1,H, i.sub.1,V)=(0,0) and four different values for p.sub.1 and p.sub.2.

(353) FIG. 30 illustrates the subset restriction 300 on rank-1 i.sub.2 according to the embodiments of the present disclosure. The embodiment shown in FIG. 30 is for illustration only. Other embodiments could be used without departing from the scope of the present disclosure.

(354) Depending on the values of parameters L.sub.1 and L.sub.2, subset restriction on rank-1 i.sub.2 indices can be differently applied. The codebook subset restriction on rank-1 i.sub.2 indices is illustrated in terms of parameters L.sub.1 and L.sub.2, with an assumption that the master codebook has rank-1 i.sub.2 indices corresponding to beam grid 1210: (L.sub.1, L.sub.2)=(4,4).

(355) In this case, the master codebook for i.sub.2 comprises 16 beams, spanned by 4×4 beams in the first and the second dimension s. In some embodiments, the index h and v in the figure corresponds to i.sub.2,1 and i.sub.2,2. The shaded squares represent the rank-1 i.sub.2 (or i.sub.2,1 and i.sub.2,2) indices that are obtained after subset restriction and the white squares represent the indices that are not included. In the figure, 1210, 1220, 1230, 1240, 1250 and 1260 respectively correspond to a codebook subset when (L.sub.1,L.sub.2)=(4,4), (2,4), (4,2), (1,4), (4,1) and (2,2) are configured. For example, 1050 shows that the beam group selected after the codebook subset restriction comprises four beams in the h dimension: (v=i.sub.2,2=0 and h=i.sub.2,1=0, 1, 2, 3).

(356) In one method, for each dimension, a UE is configured with beam skipping (i.e., s.sub.d), as illustrated in TABLE 22.

(357) TABLE-US-00031 TABLE 22 Beam skipping configuration table Parameters Candidate values Beam skipping (i.e., s.sub.d) 1, 2

(358) In one method, for each dimension, a UE is configured with beam spacing (i.e., s.sub.d), as illustrated in TABLE 23.

(359) TABLE-US-00032 TABLE 23 Beam spacing configuration table Parameters Candidate values Beam spacing (i.e., p.sub.d) 1, 2

(360) In one method, for both dimensions, a UE can be configured with pair of numbers of beams in a beam group (i.e., (L.sub.1, L.sub.2)), so that the UE can restrict the beam groups as illustrated in FIG. 39. In one example, the UE is configured with a beam group (i.e., (L.sub.1, L.sub.2)) in the higher-layer according to TABLE 24.

(361) TABLE-US-00033 TABLE 24 Beam group configuration table Parameters Candidate values Number of beams (L.sub.1, L.sub.2) (4, 1), (2, 2), (1, 4) (Respectively corresponding to 1240, 1250 and 1260)

(362) The motivation for these methods is to support various antenna configurations at the eNB with minimal signaling overhead. This configuration may be applied based on the codebook subset restriction in the form of a bit sequence. The bit sequence may consist of at least two bitmaps, one for i.sub.1,H and i.sub.1,V and the other for i.sub.2.

(363) Modification of the Legacy 8-Tx and 4-Tx Codebooks to Construct FD-MIMO Master Codebook and CSR

(364) In some embodiments, the antenna ports are numbered according to FIGS. 5A to 5D, in which it is assumed that the first dimension for the PMI corresponds to a longer dimension of the array and the second dimension corresponds to a shorter dimension of the array. When Q=16, the oversampled DFT vectors for the first dimension, u.sub.n, are of length 4, and the oversampled DFT vectors for the second dimension, v.sub.m, are of length 2. When Q=12, the DFT vectors for the first dimension are of length 3, and the DFT vectors for the second dimension are of length 2.

(365) In such a case, with config A in FIG. 5A to 5D, the first dimension is for the horizontal dimension and the second dimension is for the vertical dimension. The beam spacing p.sub.1 for the first dimension is selected such that a narrowly spaced beams in the first dimension comprise a beam group, and the beam spacing p.sub.2 for the second dimension is selected such that a widely spaced beams in the second dimension comprise the beam group. For example, for this operation, p.sub.1 and p.sub.2 can be chosen as: p.sub.1=1,p.sub.2=8. In addition, the total number of beams for the first and the second dimension are made the same: by selecting M′=32 and N′=32 for the two oversampled DFT vectors v.sub.m and u.sub.n. This way, the first dimension comprising 4-Tx ULA has closely spaced beams, and the second dimension comprising 2-Tx ULA has widely spaced beams.

(366) When the legacy parameters of s.sub.1=2 and s.sub.2=1 are chosen, the number of bits for the first PMI (i.sub.1,1 and i.sub.1,2) can be correspondingly determined. The range of i.sub.1,1=0,1, . . . , 15 and hence 4 bits are necessary to quantize the information when no codebook subset restriction is applied to this PMI. The range of i.sub.1,2 can be chosen to be i.sub.1,2=0,1, . . . , 31, and hence 5 bits are necessary to quantize the information when no codebook subset restriction is applied to this PMI.

(367) In order to reduce the master codebook size, new parameters can be chosen. For example, s.sub.1=2 and s.sub.2=2 are used, the range of both i.sub.1,1 and i.sub.1,2 are 0-15, and hence 4 bits are necessary to quantize each information when no codebook subset restriction is applied to this PMI.

(368) The configuration of (p.sub.1=1, p.sub.2=8) configures W1 beam group comprising closely spaced beams for the first dimension, and widely spaced beams for the second dimension. This configuration is likely to be useful for configuration B (tall array), especially when the column spacing is large, e.g., 4λ or even 10λ. In configuration B, the first dimension corresponds to azimuth, and the second dimension corresponds to elevation. Because the beam angle variation over time and frequency is wide in the azimuth domain and the TXRU HPBW in the azimuth domain is also wide (60 degrees), and hence it is likely that widely spaced azimuth beams will provide performance gain.

(369) The configuration of (p.sub.1=1, p.sub.2=1) that configures W1 beam group comprising closely spaced beams for the both dimensions is useful for configuration A (wide array). Because the TXRU elevation beam width is narrow, so the beam groups with narrowly spaced beams are likely to provide performance gain.

(370) Hence, in these embodiments, a UE may get configured with (p.sub.1=1, p.sub.2=1) if the serving eNB has wide array, and (p.sub.1=1, p.sub.2=8) if the serving eNB has tall array in the higher layer (i.e., RRC), as illustrated in TABLE 25.

(371) TABLE-US-00034 TABLE 25 Beam spacing configuration Value for an information Beam spacing element (RRC) for the 1.sup.st to configure p.sub.1 and p.sub.2 and 2.sup.nd dim (p.sub.1, p.sub.2) A first value . . . “wide array” (close, close) (1, 1) or “config A” A second value . . . “tall array” (close, wide) (1, 8) if M′ = 32; or “config B” or (1, 4) if M′ = 16

(372) In one method, the information element in TABLE 25 is defined in terms of (M, N, P) in FIG. 9, the first value may correspond to a configuration with N>M, and the second value may correspond to a configuration with N<M. When Q=16, (M,N)=(2,4) corresponds to the first value; and (4,2) corresponds to the second value.

(373) Codebook Subset Restriction Bitmap Construction for W1

(374) In some embodiments, the beam skipping s.sub.d is used for determining the bitmap {b.sub.n.sup.d,n=0, . . . , 31} for codebook subset restriction on rank-1 i.sub.1,H and i.sub.1,V: If b.sub.n.sup.d=1, UE is configured to be able to select i.sub.1,d=n for the PMI reporting; and If b.sub.n.sup.d=0, UE is configured such that the PMI and RI reporting is not allowed to correspond to precoder(s) associated with i.sub.1,d=n.

(375) In these embodiments it is assumed that (i.sub.1,1, i.sub.1,2)=(i.sub.1,H, i.sub.1,V), but the same design can apply even if (i.sub.1,1, i.sub.1,2)=(i.sub.1,V, i.sub.1,H).

(376) In one method, the UE is configured in the higher layer (RRC), which beam skipping the UE has to use to construct for each of i.sub.1,d. In one such example, the UE can be configured with either s.sub.d=2 or s.sub.d=4 for each of i.sub.1,d. Accordingly, the CSR bitmap can be constructed as in TABLE 26. It is noted that similar CSR bitmap tables can be straightforwardly constructed if other values such as 1 or 8 are also allowed to be configured for s.sub.d.

(377) In some embodiment, the number of bits to be reported for i.sub.1,d changes dependent upon the configured value of s.sub.d. In one example, when s.sub.d=2, 4 bit information is reported for i.sub.1,d; on the other hand when s.sub.d=4, 3 bit information is reported for i.sub.1,d. With reducing number of bits to feedback, the CSI decoding reliability at the eNB can be improved.

(378) TABLE-US-00035 TABLE 26 Codebook subset restriction on rank-1 i.sub.1,H and i.sub.1,V for N.sub.1 = 8, N.sub.2 = 4, o.sub.1 = o.sub.2 = 8 Number of bits assigned Number of for i.sub.1,H (or i.sub.1,V) i.sub.1,H i.sub.1,H s.sub.1 after subset (or i.sub.1,V) (or i.sub.1,V) (or s.sub.2) restriction Bitmap b.sub.n.sup.d, n = 0, . . . , 31 indices reporting 2 0, 2, 4, . . . , 30 $\hspace{1em}\{\begin{array}{cc}{b}_n^d=1,& n\mathrm{mod}2=0\\ b_n^d=0,& n\mathrm{mod}2=1\end{array}$ 16 4 4 0, 4, 8, . . . , 28 $\hspace{1em}\{\begin{array}{cc}{b}_n^d=1,& n\mathrm{mod}4=0\\ b_n^d=0,& n\mathrm{mod}4\ne 1\end{array}$  8 Alt 1: 4 Alt 2: 3

(379) Codebook Subset Restriction Bitmap Construction for W2

(380) In some embodiments, the beam spacing p.sub.d is used for determining the bitmap {g.sub.n.sup.d,n=0,1, . . . , 7} to indicate indices in a W2 beam group for rank-1 i.sub.2: if g.sub.n.sup.d=1, UE is configured to be able to select s.sub.d i.sub.1,d+n for the PMI reporting; and if g.sub.n.sup.d=0, UE is configured such that the PMI and RI reporting is not allowed to correspond to precoder(s) associated with s.sub.di.sub.1,d−n.

(381) In one method, the UE is configured in the higher layer (RRC), which beam spacing the UE has to use to construct for i.sub.2 (or each of i.sub.2,1 and i.sub.2,2). In one such example, the UE can be configured with either p.sub.d=1 or p.sub.d=2 for each of i.sub.1,d. Accordingly, the CSR bitmap can be constructed as in TABLE 26. It is noted that similar CSR bitmap tables can be straightforwardly constructed if other values are also allowed to be configured for p.sub.d.

(382) TABLE-US-00036 TABLE 27 Codebook subset restriction on W2 beam group for rank-1 i.sub.2 p.sub.1 (or p.sub.2) Beam Indices (I) Bitmap g.sub.n.sup.d, n = 0, 1, . . . , 7 1 0, 1, 2, 3 $\hspace{1em}\{\begin{array}{cc}{g}_n^d=1,& n\in I\\ g_n^d=0,& n.Math.I\end{array}$ 2 0, 2, 4, 6 $\hspace{1em}\{\begin{array}{cc}{g}_n^d=1,& n\in I\\ g_n^d=0,& n.Math.I\end{array}$

(383) For W2, i.e., for beam selection within the selected beam group and co-phase selection, four alternatives (Alt 1 through Alt 4) are considered for codebook subset restriction bitmap construction.

(384) In some embodiments (Alt 1), the number of beams in the first dimension (L.sub.1), the number of beams in the second dimension (L.sub.2), and the co-phase (c) are used for determining a bitmap {c.sub.n, n=0,1,2, . . . , 63} for codebook subset restriction on rank-1 i.sub.2 (as in TABLE 18): If c.sub.n=1, UE is configured to be able to select i.sub.2=n for the PMI reporting; and if c.sub.n=0, UE is configured such that the PMI and RI reporting is not allowed to correspond to precoder(s) associated with i.sub.2=n.

(385) When either TABLE 18 or TABLE 19 is configured as a master codebook, the CSR bitmap is can be constructed as in TABLE 28. The CSR (L.sub.1,L.sub.2)=(1,4), (4,1) and (2,2) are respectively corresponding to beam grids 1240, 1250 and 1260 in FIG. 30.

(386) TABLE-US-00037 TABLE 28 Codebook subset restriction on rank-1 i.sub.2 for N.sub.1 = 8, N.sub.2 = 4, o.sub.1 = o.sub.2 = 8 i.sub.2 after subset i.sub.2 after subset restriction restriction (I) . . . according (I) . . . according to the mater to the mater Number of codebook in codebook in Bitmap Number of bits assigned (L.sub.1, L.sub.2) TABLE 18 TABLE 19 c.sub.n, n = 0, 1, 2, . . . , 63 i.sub.2 indices for i.sub.2 reporting (4, 1) 0-3, 16-19, 32-35, 48-51 0-15 0$\hspace{1em}\{\begin{array}{cc}{c}_n=1,& n\in I\\ c_n=0,& n.Math.I\end{array}$ 16 4 (1, 4) 0-15 0-3, 16-19, 32-35, 48-51 $\hspace{1em}\{\begin{array}{cc}{c}_n=1,& n\in I\\ c_n=0,& n.Math.I\end{array}$ 16 4 (2, 2) 0-7, 16-23 0-7, 16-23 $\hspace{1em}\{\begin{array}{cc}{c}_n=1,& n\in I\\ c_n=0,& n.Math.I\end{array}$ 16 4

(387) When the UE reports i.sub.2,1, i.sub.2,2 and n in place of i.sub.2, the values that can be reported by the UE for i.sub.2,1 and i.sub.2,2 are configured to be restricted according to the table for 1240, 1250 and 1260.

(388) TABLE-US-00038 (L.sub.1, L.sub.2) i.sub.2,1 i.sub.2,2 (4, 1) 0, 1, 2, 3 0 (1, 4) 0 0, 1, 2, 3 (2, 2) 0, 1 0, 1

(389) Observing TABLE 28, we realize that with only these three choices for (L.sub.1, L.sub.2), the total number of i.sub.2's used with the subset restriction is only 32. This implies that some codewords in TABLE 18 and TABLE 19 can never be selected. Hence, we alternatively propose to reduce the size of master codebook and define the codebook subset restriction in terms of (L.sub.1, L.sub.2) accordingly.

(390) In these embodiments, master codebooks are alternatively defined as in TABLE 29 and TABLE 30, with fewer elements (32) than its counterparts (64) in TABLE 18 and TABLE 19. In this case, the codebook subset restriction can be constructed as in TABLE 31 for 1240, 1250 and 1260.

(391) TABLE-US-00039 TABLE 29 Master codebook for 1 layer CSI reporting for L.sub.1 = L.sub.2 = 4 i.sub.2 0 1 2 3 Precoder W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.,0.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.,1.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.,2.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.,3.sup.(1) i.sub.2 4 5 6 7 Precoder W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.+p.sub.2.sub.,0.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.+p.sub.2.sub.,1.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.+p.sub.2.sub.,2.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.+p.sub.2.sub.,3.sup.(1) i.sub.2 8 9 10 11 Precoder W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.+2p.sub.2.sub.,0.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.+2p.sub.2.sub.,1.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.+2p.sub.2.sub.,2.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.+2p.sub.2.sub.,3.sup.(1) i.sub.2 12 13 14 15 Precoder W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.+3p.sub.2.sub.,0.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.+3p.sub.2.sub.,1.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.+3p.sub.2.sub.,2.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.+3p.sub.2.sub.,3.sup.(1) i.sub.2 16 17 18 19 Precoder W.sub.s.sub.1.sub.i.sub.1,1.sub.+p1,s.sub.2.sub.i.sub.1,2.sub.,0.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.+p1,s.sub.2.sub.i.sub.1,2.sub.,1.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.+p1,s.sub.2.sub.i.sub.1,2.sub.,2.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.+p1,s.sub.2.sub.i.sub.1,2.sub.,3.sup.(1) i.sub.2 20 21 22 23 Precoder W.sub.s.sub.1.sub.i.sub.1,1.sub.+p1,s.sub.2.sub.i.sub.1,2.sub.+p.sub.2.sub.,0.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.+p1,s.sub.2.sub.i.sub.1,2.sub.+p.sub.2.sub.,1.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.+p1,s.sub.2.sub.i.sub.1,2.sub.+p.sub.2.sub.,2.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.+p1,s.sub.2.sub.i.sub.1,2.sub.+p.sub.2.sub.,3.sup.(1) i.sub.2 24 25 26 27 Precoder W.sub.s.sub.1.sub.i.sub.1,1.sub.+2p1,s.sub.2.sub.i.sub.1,2.sub.,0.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.+2p1,s.sub.2.sub.i.sub.1,2.sub.,1.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.+2p1,s.sub.2.sub.i.sub.1,2.sub.,2.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.+2p1,s.sub.2.sub.i.sub.1,2.sub.,3.sup.(1) i.sub.2 28 29 30 31 Precoder W.sub.s.sub.1.sub.i.sub.1,1.sub.+3p1,s.sub.2.sub.i.sub.1,2.sub.,0.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.+3p1,s.sub.2.sub.i.sub.1,2.sub.,1.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.+3p1,s.sub.2.sub.i.sub.1,2.sub.,2.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.+3p1,s.sub.2.sub.i.sub.1,2.sub.,3.sup.(1)

(392) TABLE-US-00040 TABLE 30 Master codebook for 1 layer CSI reporting for L.sub.1 = L.sub.2 = 4 i.sub.2 0 1 2 3 Precoder W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.,0.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.,1.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.,2.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.,3.sup.(1) i.sub.2 4 5 6 7 Precoder W.sub.s.sub.1.sub.i.sub.1,1.sub.+p1,s.sub.2.sub.i.sub.1,2.sub.,0.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.+p1,s.sub.2.sub.i.sub.1,2.sub.,1.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.+p1,s.sub.2.sub.i.sub.1,2.sub.,2.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.+p1,s.sub.2.sub.i.sub.1,2.sub.,3.sup.(1) i.sub.2 8 9 10 11 Precoder W.sub.s.sub.1.sub.i.sub.1,1.sub.+2p1,s.sub.2.sub.i.sub.1,2.sub.,0.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.+2p1,s.sub.2.sub.i.sub.1,2.sub.,1.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.+2p1,s.sub.2.sub.i.sub.1,2.sub.,2.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.+2p1,s.sub.2.sub.i.sub.1,2.sub.,3.sup.(1) i.sub.2 12 13 14 15 Precoder W.sub.s.sub.1.sub.i.sub.1,1.sub.+3p1,s.sub.2.sub.i.sub.1,2.sub.,0.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.+3p1,s.sub.2.sub.i.sub.1,2.sub.,1.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.+3p1,s.sub.2.sub.i.sub.1,2.sub.,2.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.+3p1,s.sub.2.sub.i.sub.1,2.sub.,3.sup.(1) i.sub.2 16 17 18 19 Precoder W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.+p.sub.2.sub.,0.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.+p.sub.2.sub.,1.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.+p.sub.2.sub.,2.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.+p.sub.2.sub.,3.sup.(1) i.sub.2 20 21 22 23 Precoder W.sub.s.sub.1.sub.i.sub.1,1.sub.+p1,s.sub.2.sub.i.sub.1,2.sub.+p.sub.2.sub.,0.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.+p1,s.sub.2.sub.i.sub.1,2.sub.+p.sub.2.sub.,1.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.+p1,s.sub.2.sub.i.sub.1,2.sub.+p.sub.2.sub.,2.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.+p1,s.sub.2.sub.i.sub.1,2.sub.+p.sub.2.sub.,3.sup.(1) i.sub.2 24 25 26 27 Precoder W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.+2p.sub.2.sub.,0.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.+2p.sub.2.sub.,1.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.+2p.sub.2.sub.,2.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.+2p.sub.2.sub.,3.sup.(1) i.sub.2 28 29 30 31 Precoder W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.+3p.sub.2.sub.,0.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.+3p.sub.2.sub.,1.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.+3p.sub.2.sub.,2.sup.(1) W.sub.s.sub.1.sub.i.sub.1,1.sub.,s.sub.2.sub.i.sub.1,2.sub.+3p.sub.2.sub.,3.sup.(1)

(393) TABLE-US-00041 TABLE 31 Codebook subset restriction on rank-1 i.sub.2 for N.sub.1 = 8, N.sub.2 = 4, o.sub.1 = o.sub.2 = 8 i.sub.2 after subset i.sub.2 after subset restriction restriction (I) . . . according (I) . . . according to the mater to the mater Number of codebook in codebook in Bitmap Number of bits assigned (L.sub.1, L.sub.2) TABLE 29 TABLE 19 c.sub.n, n = 0, 1, 2, . . . , 63 i.sub.2 indices for i.sub.2 reporting (4, 1) 0-3, 16-19, 24-31 0-15 $\hspace{1em}\{\begin{array}{cc}{c}_n=1,& n\in I\\ c_n=0,& n.Math.I\end{array}$ 16 4 (1, 4) 0-15 0-3, 16-19, 24-31 $\hspace{1em}\{\begin{array}{cc}{c}_n=1,& n\in I\\ c_n=0,& n.Math.I\end{array}$ 16 4 (2, 2) 0-7, 16-23 0-7, 16-23 $\hspace{1em}\{\begin{array}{cc}{c}_n=1,& n\in I\\ c_n=0,& n.Math.I\end{array}$ 16 4

(394) In some embodiments (Alt 2), the number of beams in the first dimension (L.sub.1), the number of beams in the second dimension (L.sub.2), and the co-phase (φ) are used for determining the bitmap {c.sub.n, n=0,1,2, . . . , 15} for codebook subset restriction on rank-1 i.sub.2, where the bitmap {c.sub.n} is a joint bitmap for (L.sub.1, L.sub.2): if c.sub.n=1, UE is configured to be able to select i.sub.2=4n+m, for all m=0,1,2,3 such that d.sub.m=1, for the PMI reporting; and if c.sub.n=0, UE is configured such that the PMI and RI reporting is not allowed to correspond to precoder(s) associated with i.sub.2=4n+m, for all m=0,1,2,3. Note that there is no subset restriction (or bitmap) for the co-phase φ. The UE may assume all four co-phase values {1,j,−1,−j} to derive rank-1 i.sub.2:

(395) An example of the bitmap is shown below in TABLE 32.

(396) TABLE-US-00042 TABLE 32 Codebook subset restriction on rank-1 i.sub.2 for N.sub.1 = 8, N.sub.2 = 4, o.sub.1 = o.sub.2 = 8 Number of bits assigned Bitmap for i.sub.2 (L.sub.1, L.sub.2) I c.sub.n, n = 0, 1, 2, . . . , 15 Number of i.sub.2 indices reporting (4, 1) 0, 4, 8, 12 $\hspace{1em}\hspace{1em}\{\begin{array}{cc}{c}_n=1,& n\in I\\ c_n=0,& n.Math.I\end{array}$ 16 (4 possible values for co-phase per selected beam pair) 4 (1, 4) 0-3 $\hspace{1em}\{\begin{array}{cc}{c}_n=1,& n\in I\\ c_n=0,& n.Math.I\end{array}$ 16 (4 possible values for co-phase per selected beam pair) 4 (2, 2) 0, 1, 4, 5 $\hspace{1em}\{\begin{array}{cc}{c}_n=1,& n\in I\\ c_n=0,& n.Math.I\end{array}$ 16 (4 possible values for co-phase per selected beam pair) 4

(397) In some embodiments (Alt 3), the number of beams in the first dimension (L.sub.1), the number of beams in the second dimension (L.sub.2), and the co-phase (φ) are used for determining the separate bitmaps {c.sub.n,n=0,1,2, . . . , 15} and {d.sub.m, m=0,1,2,3} for codebook subset restriction on rank-1 i.sub.2, where the bitmap {c.sub.n} is a joint bitmap for (L.sub.1, φ) and the bitmap {d.sub.m} is for L.sub.2: If c.sub.n=1, UE is configured to be able to select i.sub.2=16└n/4┘+(n mod 4)+4m, for all m=0,1,2,3 such that d.sub.m=1, for the PMI reporting; If c.sub.n=0, UE is configured such that the PMI and RI reporting is not allowed to correspond to precoder(s) associated with bit i.sub.2=16└n/4┘+ (n mod 4)+4m, for all m=0,1,2,3 such that d.sub.m=1; and If d.sub.m=1, UE is configured to be able to select i.sub.2=16└n/4┘+ (n mod 4)+4m, for all n=0,1,2, . . . , 15 such that c.sub.n=1, for the PMI reporting; and If d.sub.m=0, UE is configured such that the PMI and RI reporting is not allowed to correspond to precoder(s) associated with bit i.sub.2=16└n/4┘+ (n mod 4)+4m, for all n=0,1,2, . . . , 15 such that c.sub.n=1.

(398) An example of the bitmap is shown below in TABLE 33.

(399) TABLE-US-00043 TABLE 33 Codebook subset restriction on rank-1 i.sub.2 for N.sub.1 = 8, N.sub.2 = 4, o.sub.1 = o.sub.2 = 8 Number of bits Number assigned Bitmap of i.sub.2 for i.sub.2 (L.sub.1, L.sub.2) I J Bitmap c.sub.n, n = 0, 1, 2, . . . , 15 d.sub.m, m = 0, 1, 2, 3 indices reporting (4, 1)  0-15 0 $\hspace{1em}\{\begin{array}{cc}{c}_n=1,& n\in I\\ c_n=0,& n.Math.I\end{array}$ 0$\hspace{1em}\{\begin{array}{cc}{d}_m=1,& m\in J\\ d_m=0,& m.Math.J\end{array}$ 16 4 (1, 4) 0-3 0-3 $\hspace{1em}\{\begin{array}{cc}{c}_n=1,& n\in I\\ c_n=0,& n.Math.I\end{array}$ $\hspace{1em}\{\begin{array}{cc}{d}_m=1,& m\in J\\ d_m=0,& m.Math.J\end{array}$ 16 4 (2, 2)  0-3, 8-11 0, 1 $\hspace{1em}\{\begin{array}{cc}{c}_n=1,& n\in I\\ c_n=0,& n.Math.I\end{array}$ $\hspace{1em}\{\begin{array}{cc}{d}_m=1,& m\in J\\ d_m=0,& m.Math.J\end{array}$ 16 4