WO2015060880A1

WO2015060880A1 - Design and signaling of codebooks for full dimensional mimo

Info

Publication number: WO2015060880A1
Application number: PCT/US2013/066978
Authority: WO
Inventors: Joydeep Acharya; Salam Akoum; Sudhanshu Gaur
Original assignee: Hitachi, Ltd.
Priority date: 2013-10-25
Filing date: 2013-10-25
Publication date: 2015-04-30

Abstract

Example implementations described herein are directed to systems and methods for constructing codebooks for uniform planar array based base stations. The example implementations characterize the spatial correlations of the channel resulting from the uniform planar array arrangement and quantize the correlations for possible values to obtain the codebooks. The codebook utilized in the example implementations may lead to higher throughput than existing codebooks being used in long term evolution systems, for base stations utilizing a uniform planar array.

Description

DESIGN AND SIGNALING OF CODEBOOKS FOR FULL DIMENSIONAL

[0001] 'The present disclosure is directed to wireless systems, and more specifically, to the design and signaling of codebooks for wireless systems,

[0002] Downlink channel estimation by the user equipment (UE) and feedback to the base station (BS) is a component in cellular systems such as Long 'Term Evolution (LTE). 'The base station transmits reference signals that help the UE to estimate the channel. Let the channel estimate at the UE be H which is of dimension NR X NT, where NR and NT are the number of receive antennas at UE and transmit antennas at base station respectively. The base station uses a precoder before transmission to align the transmitted signal vector along the desired channel direction to maximize signal to noise ratio (SINR) or minimize interference to another UE's transmission. The UE informs the base station of what precoders to use as the UE measures the downlink channel.

[0003] Communication of data streams over multiple antennas Is provided by multiple input multiple output (MIMO) signal processing. Downlink (DL) MIMO signal processing in a cellular system, such as LTE, relies on feedback from a UE such as precoding matrix indicator (PMI) that denotes the eigendireciions of the MIMO channel. For feeding back PMI, the UE selects the index of the precoder from a pre-determined set of precoders, known to both the base station and UE, called the codebook.

[0004] For this purpose, the base station and UE shares a codebook C which is a finite collection of matrices W of size NT X r where r is called the rank indicator (RI) and takes values from the set ( 1, miniNT, NR.)}. The base station generates the codebooks and shares it with the UEs. The UE chooses a precoder by maximizing a metric such as channel norm as, PMI = max!HW!

WeC

I [0005] Each matrix W in the codebook is a precoder. For each value of r, let W be denoted by an N bit index called the preceding matrix indicator (PMI). Thus there are M = 2^Λ possible precoders for each rank, The codebook contains such codewords, which may be designed to match the average correlation structure of the channel. The average correlation depends on the structure of antenna elements in the base station. In the related art. Uniform Linear Arrays (ULA), as shown in FIG. 1, are mostly used in current base stations.

[0006] Because the ULA arrangement is a one dimensional arrangement of antenna arrays, the configuration leads to a specific average correlation of the channel which may take the form of a series of exponentials. Thus the codewords may be designed to match to the series of exponentials used to model the specific average correlation of the one dimensional arrangement of arrays. In the related art, the rank-1 codewords for a ULA system can be in the following Discrete Fourier Transform (DFTj vector form:

[0007] The angle is given by,

2π v

φ £ _where M = 2 and k = 1, · · · . M

CM

[0008] The range of angles of 0 to 360 is divided into M equal angles, oversampled by factor a and assigned to φ. The range of φ targets the range of azimuth angles between a base station and a UE. Azimuth and elevation angles characterize the position of the UE in the spherical coordinate system shown in FIG. 2, where the origin is the base station antenna array and the point (r, φ, Θ) is the location of the mobile.

[0009] To see why the above expression for rank- 1 codeword is used in the related art, consider the wave vector k in FIG. 2. FIG. 2 illustrates cartesian, cylindrical and spherical coordinate systems for a ULA system. This gives the direction of propagation of the radio waves from the base station to the UE.

[0010] The following properties of the wave vector k are observed: k - kk ^~ 1π! Ah

k., = & sin sin $

&_z■■■^■ k co Θ

[0011] Let the location of antenna element m in an antenna system he given by d_w = x_mx + y_my + z_mZ . Then the response of this antenna element is proportional to e ^iK'^d" , For the ULA arrangement in FIG. 1, the antenna element locations are given by d,„ = (ni - i)dx , It can be shown that the long term correlation for a rank-1 channel is proportional to the above antenna response for which the DFT vectors is optimal. Once the rank-1 (RI=1) codewords have been derived, the codewords for higher RIs can be constructed by Householder transformations,

[0012] Systems involving Uniform Planar Antenna arrays (UPA) as shown in FIG. 3 are increasingly replacing the ULA systems for base stations. The UPA involves an arrangement of antenna arrays that is in a two dimensional arrangement as opposed to the one dimensional arrangement of the ULA systems. By using planar arrays it can be easier to steer the transmitted beam in a desired three dimensional location. This can be applied, for example, when the various passive antenna elements in a UPA system are grouped together to form active antenna ports. This is called a full dimensional MIMO (FD-MTMQ) system. FIG. 3 illustrates a basic example where the individual elements shown could depict either passive antenna elements or active antenna ports,

[0013] From FIG. 3, let d be the distance between two antenna elements in the UPA and dp be the distance between two antenna ports. If there is one antenna element per port then dp = d. Otherwise, dp depends how the antenna elements are grouped into ports. Also in FIG. 3, assume that there are N_R antenna elements in the horizontal direction and Nv elements in the vertical direction. Thus the total number of transmit antennas is NT = N_H X Ny.

[0014] In the related art cellular base stations, the different passive antenna ports forming a MIMO transceiver are deployed in a ULA arrangement. For ULA based transceivers, the codebook is well characterized. However the ULA solutions do not take the deploying of the antenna elements at a base station in a two dimensional uniform planar array (UPA) arrangement into account. Furthermore one or more antenna elements in the UPA system may be grouped together to form an antenna port. The resulting antenna port is said to be active and the overall system is utilized as a full dimensional MIMO (FD-MIMO) system. For such systems, the related art codebooks are all ULA system based which may not be adequately implemented for a system involving codebook based feedback for different base stations with FD-MIMO.

SUMMARY

[0015] Aspects of the present disclosure involve a base station (BS). The base station may involve a plurality of antennas arranged in a uniform planar array (UPA); and a processor, configured to generate a codebook based on the arrangement of the plurality of antennas with respect to one or more user equipment (UEs) associated with the base station; and transmit instructions for downloading the generated codebook to one or more base stations in a coordinated multipoint transmission reception (CoMP) set associated with the base station.

[0016] Aspects of the present disclosure further include a system, which can involve one or more user equipment (UEs) and a base station (BS). The one or more UEs can be associated with the BS. The BS may include a plurality of antennas arranged in a uniform planar array (UPA); and, a processor, configured to generate a codebook based on the arrangement of the plurality of antennas with respect to the one or more UEs; and transmit instructions for downloading the generated codebook to one or more base stations in a coordinated multipoint transmission reception (CoMP) set associated with the BS.

[0017] Aspects of the present disclosure include a computer program containing instructions, which may include code for generating a codebook based on an arrangement of a plurality of antennas arranged in a uniform planar array (UPA) with respect to one or more user equipment, and code for transmitting instructions for downloading the generated codebook to one or more base stations in a coordinated multipoint transmission reception (CoMP) set. The computer program may be stored on a computer readable storage medium or a computer readable signal medium which can be executed by a hardware system such as a computer or a processor. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG. I illustrates uniform linear arrays based in multiple antenna transmitters in current base stations.

[0019] FIG. 2 illustrates cartesian, cylindrical and spherical coordinate systems for a ULA system.

[0020] FIG. 3 illustrates base stations with uniform planar arrays (UPA).

[0021] FIG. 4 illustrates a codebook generation module in accordance with an example implementation.

[0022] FIG. 5 illustrates an example module for calculating quantization granularity of the azimuth and elevation angles, in accordance with an example implementation.

[0023] FIG. 6 illustrates a FD-MIMO deployment scenario in accordance with an example implementation .

[0024] FIG. 7 illustrates a module for generating the vertical DFT weights in accordance with an example implementation,

[0025] FIG, 8 illustrates a module for generating the horizontal DFT vector in accordance with an example implementation.

[0026] FIG. 9 illustrates signaling for download and usage of multiple codebooks a two- stage procedure for small cell activation, in accordance with an example implementation.

[0027] FIG. 10 illustrates an example base station upon which example implementations can be implemented.

[0028] FIG. 11 illustrates an example user equipment upon which example implementations can be implemented. DETAILED DESCRIPTION OF THE DRAWINGS

[0029] The following detailed description provides further details of the figures and example implementat ons of the present application. Reference numerals and descriptions of redundant elements between figures are omitted for clarity, Terms used throughout the description are provided as examples and are not intended to be limiting. For example, the use of the term "automatic" may involve fully automatic or semi-automatic implementations involving user or administrator control over certain aspects of the implementation, depending on the desired implementation of one of ordinary skill in the art practicing implementations of the present application. The terms enhanced node B (eNodeB), small cell (SC), base station (BS) and pico cell may be utilized interchangeably throughout the example implementations. The implementations described herein are also not intended to be limiting, and can be implemented in various ways, depending on the desired implementation.

[0030] For UPA based MIMO systems, the codebooks for tJLA based ΜΪΜΟ systems may not be adequate. Hence, example implementations described herein are directed to codebooks for UPA systems. The proposed codebooks in the example implementations are based on the long term correlations of the channel which has been calculated based on the wave vector and two dimensional placements of the antenna elements.

[0031] In example implementations, there are systems and methods to construct codebooks for UPA based passive MIMO systems. These example implementations can also be extended to propose codebooks for the more general FD-MIMO systems, The parameters of the UPA (or FD-MIMO) systems and also the location statistics of the users to be served can be utilized to derive the codebooks.

[0032] For the codebooks are constructed in the example implementations, there is a possibility that different base stations can have different codebooks. The example implementations thereby facilitate systems for base stations having different codebooks and allow for interactions between base stations such that the base stations can store multiple codebooks with each codebook corresponding to different base stations in the coordinated multipoint transmission reception (CoMP) set. The example implementations also provide for a signaling mechanism so that LTE operations such as UE feedback can be supported for the above mentioned situation. [0033] FIG. 4 illustrates a codebook generation module in accordance with an example implementation. The codebook generation module can be implemented in a processor of a base station to generate a codebook based on the configuration of the antennas in the UP A arrangement and the UEs associated with the base station, The descriptions of these modules are described herein with examples of specific implementations for UP A with passive antenna arrays and UPA with active antenna arrays (example of FD-MIMO), The codebook generation module may include four modules C1 -C4 which can be configured to perform various functions as described below.

Module CI: Generates quantized azimuth and elevation angle values

[0034] Let the codebook be of N bits. Thus there are M = 2^N codewords. As described below in Module C4, these different codewords correspond to different values of the azimuth and elevation angles. Thus Module CI is configured to calculate these different azimuth and elevation angles. Details of example Module CI are provided in FIG. 5.

[0035] FIG. 5 is a module for calculating quantization granularity of the azimuth and elevation angles, in accordance with an example implementation. In a flow for Module CI for FIG. 5 the range of azimuth angles and elevation angles are estimated for all UEs that need to be served as shown at 501 and 502. The azimuth and elevation angles can be based on location information provided by the UEs or by other methods depending on the desired implementation. The ratio ε is calculated as shown at 503. Based on the calculated ratio, the azimuth angle and the elevation angle are quantified as codewords as shown at 504. The total number of azimuth angles and elevation angles are evaluated as equally spaced angles from a range, which can be stored in a memory of the base station. This is shown at 505 and 506.

[0036] Provided below are examples of implementations of Module CI. For passive antenna arrays, dynamic beam steering on the transmitted waveforms may not be performed. Hence the ranges of the azimuth and elevation angles are as follows: a) For a base station in a given sector, the azimuth angles of all UEs located in that sector varies from 0 to 120 degrees. Hence a possible example can be cp_R = {30, 150} for the first sector, { 150, 270} for the second and {270, 30} for the third. b) For a base station in a given sector, the elevation angles of all UEs located in that sector varies from 0 to 180 degrees. Hence ( - 180 degrees, c) Thus ε = 120/(120 + 180) = 0.4 -0.5, Let N = 4. Hence Np ~ Nt = 2, Thus there are 4 azimuth angles in cps spaced 120/4 = 30 degrees apart (i.e. { 30, 60, 90, 120} for the first sector and so on) and 4 elevation angles spaced 180/4 ^~ 45 degrees apart in O_S (i.e. { 0, 45, 90, 135 })

[0037] For active antenna based FD-MIMG systems, dynamic beam steering of the transmit waveform is possible to direct the beam towards any specific three dimensional spatial region. This is illustrated in FIG. 6, which illustrates a FD-MIMO deployment scenario in accordance with an example implementation, In the example of FIG, 6, the macro cell and the pico cell each have their own beams which can be dynamically steered or modified based on the azimuth and the elevation angle. Let the main lobe of the FD-MIMO beam point towards angles azimuth and elevation angles ( Los and O and let the respective half power beam widths be (pHPBW and OHPBW respectively. This is illustrated in FIG. 6 for the macro cell. The main lobe direction and the half power beam widths of a FD-MIMO system depend on the number of antenna elements constituting an antenna port and the electrical tilt applied to the antenna ports.

[0038] Module CI calculates the possible ranges, which are: a) φ_κ = { ⁽pLos - ⁽ HPBW , fpLoS + ⁽pHPBW ] b) O = { O S - 0HPBW , O S + Ot-iPBW } c) ε - (pHPBw /( (pHPBW + OHPBW)- The actual angles are calculated based In a

similar fashion to the passive UP A configuration.

[0039] FIG. 7 illustrates a module for generating the vertical DFT weights in accordance with an example implementation. This module generates complex phases or weights that capture the effect of having antenna ports in the vertical dimension. The DFT to represent the antennas in a vertical manner is shown at 701, wherein dp is utilized for the distances between active antenna ports and cos Θ is representative of the elevation of the antenna with respect to one or more of the associated UEs, As shown at 702, the vertical configuration of the antennas and the elevation with respect to the one or more associated UEs is utilized in providing weights. Other factors can also he utilized depending on the desired implementation, such as transmit power and so on. Thus the resulting DFT for the vertical configuration differs from that of the ULA systems, which is a one dimensional arrangement that may not take elevation into consideration.

Module

[0040] FIG. 8 illustrates a module for generating the horizontal DFT vector in accordance with an example implementation. This module generates the DFT vectors that capture the effect of having an antenna array in the horizontal domain. Because azimuth is taken into account to facilitate a two dimensional configuration, the resulting DFT for the horizontal configuration also differs from that of the ULA systems, which is a one dimensional arrangement that may not take azimuth into consideration. The DFT to represent the antennas in a horizontal manner as shown at 801, wherein dp is utilized for the distances between active antenna ports and cos(^) sin($) is representative of the azimuth of the antenna with respect to one or more of the associated UEs. As shown at 802, the vector is generated based on the DFT determined at 801.

Module C4: Computes the codewords

[0041] Module C4 then computes the codewords for generating the codebook. The structure of a codeword is now given by

¾>·{ø, 0) = [v(l)w^? ,ν(2 /^Γ , · · ·ν(Αν - 1)// ]'

[0042] The different codewords are calculated by substituting values of φ and Θ that were derived in Module CI. The resulting codewords are then utilized to generate the codebook for the base station.

Downloading and Usage of Multiple Codebooks at a IJE

[0043] In an example implementation, each base station in a CoMP set may have its own codebook generation module. In such an implementation, each base station may thereby generate its own codebook, thereby resulting in the possibility of having different codebooks among base stations in the CoMP set. This is because for base stations with FD-MIMO, the codebook may depend on the beam directions and half power beam widths. The beam parameters may be different for the base stations within the CoMP depending on what user profile they are trying to serve. An example of this is given in FIG 6. 'The macro cell is configured to cover a large number of UEs (e.g. all the UEs in the building) and hence has a wide half power beam width and a main lobe pointing towards a direction to maximize the coverage, By contrast the pico cell has a small and specific profile of UEs that it targets for transmission (e.g., the UEs in the lower floors of the building). The main lobe of the pico beam will be pointed towards these UEs and it would have a narrow half power beam width. Thus the codebooks of the macro and pico may be different. This situation is in contrast to the related art cellular systems as all base stations in the related art have the same codebooks.

[0044] One way to yield higher gains in such scenarios is to use FD-MIMO along with base station cooperation technology such as CoMP. To facilitate CoMP, the UE has to feed back PMIs of multiple base stations such as the macro and pico in FIG 6. Hence the UE has to store different codebooks corresponding to the different base stations and also know when to use the appropriate codebooks. This is also a new situation that does not arise in current cellular systems.

[0045] FIG. 9 illustrates signaling for download and usage of multiple codebooks a two- stage procedure for small cell activation, in accordance with an example implementation. The example implementation of FIG. 9 facilitates a signaling method to permit a UE to download and use multiple codebooks.

[0046] In the example implementation of FIG. 9, the serving base station contains a codebook generation module 901, a codebook transmission module 902 and a joint reference signal and cell-ID encoding and transmitter module 903. The codebook generation module 901 can be configured as described above. The codebook transmission module 902 is configured to transmit instructions for downloading the generated codebook to one or more base stations in the CoMP set associated with the base station. The codebook transmission module 902 can also be used to receive instructions for downloading a codebook from one or more base stations in the CoMP set and process the instructions to download the codebook from the corresponding base station. The joint reference signal and cell-ID encoding and transmitter module 903 is configured to generate and transmit a reference signal to one or more UEs along with a cell-ID that acts as an identifier for the reference signal to indicate which base station is transmitting the reference signal.

[0047] The non-serving base station can also include the same configuration of modules as the serving base station, denoted as 901-1 and 903-1. In the example of FIG. 9, the codebook transmission module 902 is omitted for the non-serving base station to indicate that it is the non-serving base station. However, when the non- serving base station serves as the serving base station, the non-serving base station can facilitate codebook transmission with its own codebook transmission module.

[0048] Further, the UE contains a codebook storage module 904, a joint reference signal and cell-ID decoder module 905 and a channel estimation and feedback module 906. The codebook storage module 904 is configured to store one or more codebooks associated with one or more base stations. The joint reference signal and cell-ID decoder module 905 is configured to decode the reference signal and the cell- ID associated with the reference signal. The channel estimation and feedback module is configured to estimate the channel and provide channel estimation feedback to one or more base stations,

[0049] The signaling flow for the example of FIG. 9 is as follows. At 910 and 910-1, the base stations generate codebooks individually as per the example implementations described above. Each base station in a CoMP set of base stations shares their codebooks with all others in the set (e.g. via backhaul), At 920, each UE has a serving base station which is responsible for all control information and initial access. The serving base station transmits the codebooks of all the base stations in the CoMP set to the UE. The UE stores all the codebooks in the codebook storage module 904 (e.g. a memorv unit). When the serving base station transmits a codebook, it also transmits the cell-ID of the corresponding base station. At 930 and 930-1, for purposes of channel estimation, a base station transmits reference signals (e.g. such as channel state interference reference signal (CSI-RS)). The base station also transmits its cell- ID. The inclusion of the cell-ID is different from the CSI-RS configuration for CoMP in the related art, where the reference signal may not contain the cell-ID information. Further, systems in the related art that can be configured to utilize the cell-ID are not used to select different codebooks. The example implementations of the present disclosure thus ensure UE- specific reference signal configuration while also retaining the cell- ID information so that the UE can decode it. This could be implemented in multiple ways such as including the cell-ID information while configuring the CSI-RS resource for a UE. At 940, once the UE has figured the cell-ID in the received reference signal, the UE sends a query to the codebook storage module 904 to retrieve the codebook corresponding to the base station with that cell-ID, At 950, the UE performs channel estimation and feedback utilizing the obtained codebook.

[0050] FIG. 10 illustrates an example base station upon which example implementations can be implemented, The block diagram of a base station 1000 in the example implementations is shown in FIG. 10, which could be a macro base station or a pico base station. The base station 1000 may include the following modules: the Central Processing Unit (CPU) 1001 , the baseband processor 1002, the transmission/receiving (Tx/Rx) array 1003, the Xn interface 1004, and the memory 1005. The CPU 1001 is configured to execute one or more modules as described, for example, in FIG. 4 and FIG, 9. The baseband processor 1002 generates baseband signaling including the reference signal and the system information such as the cell-ID information. The Tx/Rx array 1003 contains an array of antennas which are configured in a UP A configuration to facilitate communications with associated UEs. The antennas may be grouped arbitrarily to form one or more active antenna ports. Associated UEs may communicate with the Tx/Rx array to request the corresponding codebook when the UE is switching to a different base station in the CoMP set. The Xn interface 1104 is used to exchange traffic and interference information between two base stations via a backhaul to transmit instructions for downloading codebooks or for receiving codebooks from other base stations within the CoMP set. The memory 1005 is configured to store codebooks. Memory 1105 may take the form of a computer readable storage medium or can be replaced with a computer readable signal medium as described below. The detailed functions of each module are explained below.

[0051] FIG. 11 illustrates an example user equipment upon which example implementations can be implemented, The UE 1100 may involve the following modules: the CPU module 1 101, the channel estimator 1102, the baseband processor 1 103, and the memory 1104. The CPU module 1101 can be configured to perform one or more functions, such as execution of the modules described in FIG. 9. The channel estimator 1 102 can be configured to perform the channel estimation, and save the channel estimate in the memory 1 104 and also request a codebook for storage in the memory 1104, The baseband digital signal processing (DSP) module can be configured to perform one or more functions, such as to generate the Positioning RS (PRS) for the serving base station to estimate the location of the UE as described in FIG. 9. The memory 1 104 can be configured to store the most recent channel estimate, as well as one or more codebooks retrieved from the serving base station. When the UE 1100 switches to a different base station, the UE can then utilize the corresponding codebook of the different base station,

[0052] Finally, some portions of the detailed description are presented in terms of algorithms and symbolic representations of operations within a computer. These algorithmic descriptions and symbolic representations are the means used by those skilled in the data processing arts to most effectively convey the essence of their innovations to others skilled in the art. An algorithm is a series of defined steps leading to a desired end state or result. In example implementations, the steps carried out require physical manipulations of tangible quantities for achieving a tangible result.

[0053] Unless specifically stated otherwise, as apparent from the discussion, it is appreciated that throughout the description, discussions utilizing terms such as "processing," "'computing," "calculating," "determining," "displaying," or the like, can include the actions and processes of a computer system or other information processing device that manipulates and transforms data represented as physical (electronic) quantities within the computer system's registers and memories into other data similarly represented as physical quantities within the computer system's memories or registers or other information storage, transmission or display devices.

[0054] Example implementations may also relate to an apparatus for performing the operations herein. This apparatus may be specially constructed for the required purposes, or it may include one or more general-purpose computers selectively activated or reconfigured by- one or more computer programs. Such computer programs may be stored in a computer readable medium, such as a computer-readable storage medium or a computer-readable signal medium. A computer-readable storage medium may involve tangible mediums such as, but not limited to optical disks, magnetic disks, read-only memories, random access memories, solid state devices and drives, or any other types of tangible or non-transitory media suitable for storing electronic information. A computer readable signal medium may include mediums such as carrier waves. The algorithms and displays presented herein are not inherently related to any particular computer or other apparatus. Computer programs can involve pure software implementations that involve instructions that perform the operations of the desired implementation.

[0055] Various general-purpose systems may be used with programs and modules in accordance with the examples herein, or it may prove convenient to construct a more specialized apparatus to perform desired method steps. In addition, the example implementations are not described with reference to any particular programming language. It will be appreciated chat a variety of programming languages may be used to implement the teachings of the example implementations as described herein. The instructions of the programming language(s) may be executed by one or more processing devices, e.g., central processing units (CPUs), processors, or controllers.

[0056] As is known in the art, the operations described above can be performed by hardware, software, or some combination of software and hardware. Various aspects of the example implementations may be implemented using circuits and logic devices (hardware), while other aspects may be implemented using instructions stored on a machine-readable medium (software ), which if executed by a processor, would cause the processor to perform a method to carry out implementations of the present application. Further, some example implementations of the present, application may be performed solely in hardware, whereas other example implementations may be performed solely in software. Moreover, the various functions described can be performed in a single unit, or can be spread across a number of components in any number of ways. When performed by software, the methods may be executed by a processor, such as a general puipose computer, based on instructions stored on a computer-readable medium. If desired, the instructions can be scored on the medium in a compressed and/or encrypted format.

[0057] Moreover, other implementations of the present application will be apparent to those skilled in the art from consideration of the specification and practice of the teachings of the present application. Various aspects and/or components of the described example implementations may be used singly or in any combination. It is intended that the specification and example implementations be considered as examples only, with the true scope and spirit of the present application being indicated by the following claims.

Claims

CLAIMS What is claimed is:

1. A base station (BS), comprising:

a plurality of antennas arranged in a uniform planar array (UP A); and, a processor, configured to:

generate a codebook based on the arrangement of the plurality of antennas with respect to one or more user equipment (UEs) associated with the BS; and

transmit instructions for downloading the generated codebook to one or more base stations in a coordinated multipoint transmission reception (CoMP) set associated with the BS.

2. The BS of claim 1, wherein the codebook comprises codewords based on an azimuth angle and an elevation angle of the plurality of antennas with respect to the one or more UEs associated with the base station,

3. The BS of claim 2, wherein the codebook comprises weights based on the azimuth angle and the elevation angle.

4. The BS of claim 1, wherein the processor is further configured to download at least one more codebook from at least one of the one or more base stations in the CoMP set.

5. The BS of claim 1, wherein the plurality of antennas are grouped into one or more active antenna ports, and wherein the generated codebook is based on the grouping.

6. The BS of claim 1, wherein the generated codebook is configured to be utilized by the one or more UEs associated with the base station for switching to one of the one or more base stations in the Co P set based on a cell identifier.

7. A computer program containing instructions for a base station (BS), the instructions comprising:

code for generating a codebook based on an arrangement of a plurality of antennas arranged in a uniform planar array (UP A) with respect to one or more user equipment (UE) associated with the BS; and

code for transmitting instructions for downloading the generated codebook to one or more base stations in a coordinated multipoint transmission reception (CoMP) set associated with BS.

8. The computer program of claim 7, wherein the codebook comprises codewords based on an azimuth angle and an elevation angle of the plurality of antennas with respect to the one or more UEs associated with the BS.

9. The computer program of claim 8, wherein the codebook comprises weights based on the azimuth angle and the elevation angle.

10. The computer program of claim 7, wherein the instructions further comprise code for downloading at least one more codebook from at least one of the one or more base stations in the CoMP set.

11. The computer program of claim 7, wherein the plurality of antenna arrays are grouped into one or more active antenna ports, and wherein the generated codebook is based on the grouping.

12. The computer program of claim 7, wherein the generated codebook is

configured to be utilized by the one or more UEs associated with the base station for switching to one of the one or more base stations in the CoMP set based on a cell identifier.

13. A system, comprising:

one or more user equipment (UEs) and a base station (BS), wherein the one or more UEs are associated with the base station, the BS compr sing:

a plurality of antennas arranged in a uniform planar array (UPA); and, a processor, configured to:

generate a codebook based on the arrangement of the plurality of antennas with respect to the one or more UEs; and

14, The system of claim 13, wherein the one or more UEs are configured to utilize the generated codebook to switch to one of the one or more base stations in the CoMP set based on a cell identifier.

15. The system of claim 13, wherein the processor is further configured to

download at least one more codebook from at least one of the one or more base stations in the CoMP set.