WO2017193731A1 - 信道状态信息反馈方法、预编码方法、终端设备和基站 - Google Patents

信道状态信息反馈方法、预编码方法、终端设备和基站 Download PDF

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Publication number
WO2017193731A1
WO2017193731A1 PCT/CN2017/079346 CN2017079346W WO2017193731A1 WO 2017193731 A1 WO2017193731 A1 WO 2017193731A1 CN 2017079346 W CN2017079346 W CN 2017079346W WO 2017193731 A1 WO2017193731 A1 WO 2017193731A1
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Prior art keywords
antennas
matrix
base station
codebook
terminal device
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PCT/CN2017/079346
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English (en)
French (fr)
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武露
韩玮
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华为技术有限公司
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Priority to EP17795349.4A priority Critical patent/EP3444959B1/en
Publication of WO2017193731A1 publication Critical patent/WO2017193731A1/zh
Priority to US16/186,433 priority patent/US10498423B2/en

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/002—Reducing depolarization effects
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0413—MIMO systems
    • H04B7/0417—Feedback systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0413—MIMO systems
    • H04B7/0456—Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0413—MIMO systems
    • H04B7/0456—Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting
    • H04B7/046—Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting taking physical layer constraints into account
    • H04B7/0469—Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting taking physical layer constraints into account taking special antenna structures, e.g. cross polarized antennas into account
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0413—MIMO systems
    • H04B7/0456—Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting
    • H04B7/0478—Special codebook structures directed to feedback optimisation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
    • H04B7/0615—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
    • H04B7/0619—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal using feedback from receiving side
    • H04B7/0621—Feedback content
    • H04B7/0626—Channel coefficients, e.g. channel state information [CSI]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
    • H04B7/0615—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
    • H04B7/0619—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal using feedback from receiving side
    • H04B7/0636—Feedback format
    • H04B7/0639—Using selective indices, e.g. of a codebook, e.g. pre-distortion matrix index [PMI] or for beam selection

Definitions

  • the present invention relates to a multi-antenna technology, and in particular, to a channel state information feedback method, a precoding method, a terminal device, and a base station.
  • MIMO Multiple Input Multiple Output
  • FIG. 1 is a schematic diagram of an application scenario of MIMO.
  • the application scenario shown in FIG. 1 includes a transmitting device 102 and a receiving device 104.
  • the transmitting device 102 can be, for example but not limited to, a base station.
  • the receiving device 104 can be, for example but not limited to, a terminal device.
  • the transmitting device 102 is configured with n (n>1) transmitting antennas, specifically as transmitting antennas 1 to n.
  • the receiving end device 104 is configured with m (m>1) receiving antennas, specifically shown as receiving antennas 1 to m. In this way, m ⁇ n channels exist between the n transmit antennas and the m receive antennas, as shown by solid lines between the transmit antennas 1 to n and the receive antennas 1 to m (partial channels are not shown). .
  • the above m ⁇ n channels can be represented by the following channel matrix:
  • h ij (1 ⁇ i ⁇ m, 1 ⁇ j ⁇ n) represents the channel gain of the channel between the transmitting antenna j and the receiving antenna i.
  • the receiving end device 104 can determine the above channel matrix by using a pilot (Pilot) transmitted by the transmitting end device 102.
  • the above m ⁇ n channels may be equivalent to i channels independent of each other.
  • These channels also known as beams, can be obtained by a variety of techniques, such as precoding (Precoding) techniques.
  • the precoding technique defines the beam through a Precoding Matrix.
  • each column vector (also referred to as a precoding vector) of the precoding matrix corresponds to one beam.
  • the elements of the column vector correspond to the antenna (or the antenna port (Antenna Port)). It is used to weight the antennas so that the signals transmitted by the antennas are superimposed on each other to form a beam.
  • the maximum number of terminal device beams is equal to the number of singular values of the channel matrix, ie the rank of the channel matrix (Rank). When the partial singular value is too small (below the preset threshold), the number of singular values whose value is too small can also be subtracted from the above number.
  • the number of channels independent of each other is represented by the rank of the channel matrix.
  • the precoding technique uses a preset codebook to record the precoding matrix.
  • the receiving end device 104 selects an appropriate codeword in the codebook to represent the pre-based according to the foregoing channel matrix, based on a preset selection criterion (such as, but not limited to, a maximum channel capacity criterion, a minimum mean square error criterion, or a minimum singular value criterion, etc.).
  • a preset selection criterion such as, but not limited to, a maximum channel capacity criterion, a minimum mean square error criterion, or a minimum singular value criterion, etc.
  • the existing codebook is designed for the Line Of Sight (LOS) channel, but the actual channel is often a Non Line of Sight (NLOS) channel. Therefore, the precoding matrix of the NLOS channel is determined based on the LOS codebook, and the accuracy is very limited.
  • LOS Line Of Sight
  • NLOS Non Line of Sight
  • a precoding method is provided to improve the accuracy of the existing precoding matrix.
  • a terminal device is provided to improve the accuracy of the existing precoding matrix.
  • a base station is provided to improve the accuracy of the existing precoding matrix.
  • a channel state information CSI feedback method including:
  • a precoding method comprising:
  • CSI channel state information
  • the CSI is generated by the terminal device according to a precoding matrix generated by the terminal device according to a channel matrix and a base codebook
  • the channel matrix is generated by the terminal device according to the pilot
  • the modulation symbols that need to be transmitted to the terminal device are precoded according to the precoding matrix.
  • a terminal device including:
  • a receiving module configured to receive a downlink symbol from a base station
  • a channel state information CSI generating module configured to obtain a channel matrix according to the pilot included in the downlink symbol, calculate a precoding matrix according to the channel matrix and the base codebook, and generate CSI according to the precoding matrix;
  • a transmitting module configured to send an uplink symbol to the base station, where the CSI is carried in the uplink symbol.
  • a base station including:
  • a transmitting module configured to send a downlink symbol to the terminal device, where the downlink symbol carries a pilot
  • a receiving module configured to receive channel state information CSI from a terminal device, where the CSI is generated by the terminal device according to a precoding matrix, where the precoding matrix is generated by the terminal device according to a channel matrix and a base codebook, where a channel matrix is generated by the terminal device according to the pilot;
  • a precoding module configured to generate a precoding matrix according to the CSI, and precode the modulation symbols that need to be sent to the terminal device according to the precoding matrix.
  • the base station is configured with an antenna array
  • the basic codebook is:
  • W is the basic codebook
  • W 1 is a beam codebook
  • the number of rows is equal to the number of antennas of the base station
  • W 2 is a weighted combined codebook
  • G corresponds to a first set of antennas in the antenna array, and G' corresponds to a second set of antennas in the antenna array;
  • the matrices A and B are column vectors, and the number of non-zero elements included in the column vectors A and B are both greater than 1; the number of elements included in the column vector A is equal to the number of column vectors in the matrix G, and the column vector B contains The number of elements is equal to the number of column vectors in the matrix G'.
  • the antenna array includes 2N 1 N 2 antennas, and the first group antenna and the second group antenna each include N 1 N 2 antennas, and
  • ⁇ is a preset set of N 1 N 2 ⁇ 1 order vectors which are orthogonal or non-orthogonal to each other, L is the number of vectors and L ⁇ 2N 1 N 2 ; the column vectors in G are orthogonal or non-positive to each other The column vectors in G' are orthogonal or non-orthogonal to each other;
  • ⁇ is the value of the cross-polarization leakage between the polarization direction of the second set of antennas and the polarization direction of the first set of antennas
  • ⁇ is the phase rotation angle of the second set of antennas relative to the first set of antennas, ⁇ i and As a default,
  • G is the same as or different from G'; A is the same as or different from B.
  • the column vectors in G and G' may be selected from the same column vector set, or may be selected from different column vector sets.
  • the order of the column vectors from the same column vector set is the same, and the order of the column vectors from different column vector sets may be the same or different.
  • the polarization directions of the antennas in each group of antennas are the same, and the polarization directions of the first group antennas may be the same as or different from the polarization directions of the second group antennas.
  • the technical solution provided by the embodiment of the present invention selects multiple beams for each group of antennas to perform weighted combination, thereby constructing a new beam, and weighting the set of antennas by using the new beam.
  • the new beam constructed can more accurately simulate the real environment of the channel and improve the accuracy of precoding.
  • FIG. 1 is a schematic diagram of an application scenario of MIMO
  • FIG. 2 is a schematic diagram of a MIMO equivalent channel
  • FIG. 3 is an exemplary schematic diagram of a wireless communication network in accordance with an embodiment of the present invention.
  • FIG. 4 is a schematic diagram of a CSI feedback process according to an embodiment of the invention.
  • FIG. 5A is an exemplary schematic diagram of an antenna array according to an embodiment of the invention.
  • 5B is an exemplary schematic diagram of a first group of antennas in the antenna array shown in FIG. 5A;
  • 5C is an exemplary schematic diagram of a second set of antennas in the antenna array shown in FIG. 5A;
  • FIG. 6 is an exemplary flowchart of a CSI feedback method according to an embodiment of the invention.
  • FIG. 7 is an exemplary flow chart of a precoding method in accordance with an embodiment of the present invention.
  • FIG. 8 is a schematic structural diagram of hardware of a terminal device according to an embodiment of the invention.
  • FIG. 9 is a schematic diagram showing the hardware structure of a base station according to an embodiment of the present invention.
  • the above wireless communication technologies include, but are not limited to, Time Division Multiple Access (TDMA) technology, Frequency Division Multiple Access (FDMA) technology, Code Division Multiple Access (CDMA) technology, and time division.
  • TDMA Time Division Multiple Access
  • FDMA Frequency Division Multiple Access
  • CDMA Code Division Multiple Access
  • time division Time Division-Synchronous Code Division Multiple Access
  • OFDMA Orthogonal Frequency Division Multiple Access
  • SC-FDMA single carrier frequency division multiple access
  • SDMA Space Division Multiple Access
  • the above wireless communication technology is adopted as a radio access technology (RAT) by many wireless communication standards, thereby constructing various wireless communication systems (or networks) well known today, including but not limited to Global System for Mobile Communications (GSM), CDMA2000, Wideband CDMA (WCDMA), WiFi defined by the 802.11 series of standards, Worldwide Interoperability for Microwave Access (WiMAX), long-term Evolution (Long Term Evolution, LTE), LTE-Advanced (LTE-A), and evolution systems of these wireless communication systems.
  • GSM Global System for Mobile Communications
  • WCDMA Wideband CDMA
  • WiFi defined by the 802.11 series of standards
  • WiMAX Worldwide Interoperability for Microwave Access
  • LTE long-term Evolution
  • LTE-A LTE-Advanced
  • evolution systems of these wireless communication systems evolution systems of these wireless communication systems.
  • FIG. 3 is an exemplary schematic diagram of a wireless communication network 300 in accordance with an embodiment of the present invention.
  • the wireless communication network 300 includes base stations 302-306 and terminal devices 308-322, wherein the base stations 302-306 can pass each other through a backhaul link (such as a line between base stations 302-306).
  • the communication is performed, and the backhaul link may be a wired backhaul link (such as fiber optic cable or copper cable) or a wireless backhaul link (such as microwave).
  • the terminal devices 308-322 can communicate with the base stations 302-306 over a wireless link (as indicated by the broken lines between the base stations 302-306 and the terminal devices 308-322).
  • the base stations 302-306 are configured to provide wireless access services for the terminal devices 308-318.
  • each base station provides a service coverage area (also referred to as a cell, as shown in each ellipse area in FIG. 3), and the terminal device entering the area can communicate with the base station by using a wireless signal to receive the base station.
  • Wireless access service provided.
  • the service coverage areas of the base stations 302, 304, and 306 have a common overlapping area, and the terminal device 320 is within the overlapping area, so the terminal device 320 can receive the base station 302. 304 and 306 wireless signals.
  • the base station may be referred to as a Node B (NodeB), an evolved Node B (eNodeB), and an Access Point (AP), etc., depending on the wireless communication technology used.
  • NodeB Node B
  • eNodeB evolved Node B
  • AP Access Point
  • the base station can be further divided into macro cells (Macro) A macro base station of a cell, a micro base station for providing a pico cell, and a femto base station for providing a femto cell.
  • macro macro base station of a cell
  • micro base station for providing a pico cell
  • femto base station for providing a femto cell.
  • future base stations may use other names.
  • the terminal devices 308-318 may be various wireless communication devices having wireless communication functions, such as but not limited to mobile cellular phones, cordless phones, personal digital assistants (PDAs), smart phones, notebook computers, tablets, wireless devices.
  • IOT Internet of Things
  • the communication unit obtains a wireless communication function so that it can access the wireless communication network and accept remote control.
  • Such devices have wireless communication functions because they are equipped with wireless communication units, and therefore belong to the category of wireless communication devices.
  • the terminal devices 308-318 may also be referred to as mobile stations, mobile devices, mobile terminals, wireless terminals, handheld devices, clients, and the like.
  • Base stations 302-306 and terminal devices 308-322 can be configured with multiple antennas to support MIMO technology. Further, the terminal devices 308-322 can support single-user MIMO (SU-MIMO), and can also support multi-user MIMO (Multi-User MIMO, MU-MIMO) by means of SDMA technology.
  • the base station 302-306 and the terminal devices 308-322 can also flexibly support single input single output (SISO) technology, single input multiple output (SIMO) and multiple input.
  • SISO single Input Single Output
  • SIMO Receive Diversity
  • TD Transmit Diversity
  • base station 302 and terminal devices 304-310 can employ various wireless communication technologies for communication, such as, but not limited to, the various wireless communication technologies mentioned above.
  • the wireless communication network 300 shown in FIG. 3 is for example only and is not intended to limit the technical solution of the present invention.
  • the wireless communication network 300 further includes other devices, such as but not limited to a base station controller (BSC), and may also configure the base station and the terminal device according to specific needs. .
  • BSC base station controller
  • the terminal device feeds back channel state information (CSI) to the base station, and the base station adjusts the wireless signal that needs to be sent to the terminal device according to the CSI, so as to implement more on the terminal device side. Good reception.
  • CSI channel state information
  • FIG. 4 is a schematic diagram of a CSI feedback process in accordance with an embodiment of the present invention.
  • the CSI feedback process is performed between the base station 402 and the terminal device 404.
  • the base station 402 specifically includes a transmitting module 4022, a receiving module 4024, and a precoding module 4026.
  • the terminal device 404 specifically includes a receiving module 4042, a CSI generating module 4044, and a transmitting module 4046.
  • the specific process of CSI feedback is as follows.
  • the transmitting module 4022 of the base station 402 transmits a downlink symbol 406, and the downlink symbol 406 carries a pilot 4062.
  • the downlink symbol 406 may be, for example but not limited to, an Orthogonal Frequency-Division Multiplexing (OFDM) symbol.
  • An OFDM symbol is usually obtained by weighting and summing a set of subcarriers (Sub-carriers), and the weight of the subcarriers is The modulation symbol to be transmitted (generally a complex number), including the pilot.
  • the receiving module 4024 of the terminal device 404 receives the downlink symbol 406 described above.
  • the CSI generation module 4044 of the terminal device 404 obtains a channel matrix based on the pilots 4062 included in the downlink symbol 406.
  • the CSI generation module 4044 determines an appropriate precoding matrix according to the above channel matrix and the base codebook, and generates CSI according to the precoding matrix.
  • Base codebook LTE-Advanced with an embodiment of the present invention a codebook similar, two-stage codebook structure, a long-term and / or broadband codebook W 1, two short-term and / or narrowband codebook W 2 . Both W 1 and W 2 are matrices and both have multiple values.
  • the base codebook W is the product of the matrix W 1 and W 2 , so the base codebook W is also a matrix and also has a plurality of values, each of which is a precoding matrix.
  • the base codebook W provided by the embodiment of the present invention will be described in more detail below in conjunction with FIGS. 5A-5C.
  • the method of determining the precoding matrix by LTE-Advanced can be referred to to determine the precoding matrix according to the channel matrix and the base codebook.
  • Several common methods are listed below to illustrate the determination process of the precoding matrix. Those skilled in the art should understand that these methods are only used as examples and are not intended to limit the scope of the present invention. In the specific implementation process, other methods may also be used to determine the precoding matrix.
  • a commonly used method for determining a precoding matrix is to traverse all the values of the matrices W 1 and W 2 to obtain all combinations of W 1 and W 2 , and thereby calculate all the values of the base codebook W, and then according to the channel.
  • the matrix selects a precoding matrix that meets a preset selection criterion from all the values of the basic codebook W, and carries an index corresponding to the values of W 1 and W 2 corresponding to the precoding matrix in the corresponding precoding matrix.
  • the indication PM Indicator, PMI
  • it can be passed To carry the index of the value of W 1 through To carry the index of the value of W 2 .
  • the values of the matrices W 1 and W 2 vary with time, and the value of W 1 changes relatively slowly, and the value of W 2 changes relatively quickly.
  • it may be considered to modify only the value of one of W 1 and W 2 while the value of the other remains unchanged, so that the calculation amount of the precoding matrix can be greatly reduced. It also reduces the CSI feedback overhead. It is not difficult to understand that the premise of implementing the above solution is that the change periods of W 1 and W 2 are different. Therefore, different feedback periods can be specified for W 1 and W 2 .
  • the value of W 1 changes slowly, it can be W 1 sets a longer feedback period; the value of W 2 changes faster, and a shorter feedback period can be set for W 2 .
  • the value of the other matrix can be extended by the previous value, and the values of W 1 and W 2 need to be stored.
  • the initial values of W 1 and W 2 can be obtained according to the former method, or the default values can be used.
  • the precoding matrix can be determined by referring to the following method.
  • the feedback period of one of W 1 and W 2 arrives, all the values of the matrix can be traversed and combined with the stored values of the matrix whose feedback period has not yet arrived, and the basic codebook is calculated. All the values of W are selected from the values according to the channel matrix, and the index corresponding to the value of the matrix corresponding to the feedback period corresponding to the precoding matrix is carried.
  • the corresponding PMI as CSI feedback.
  • each column vector of the precoding matrix corresponds to one beam, so the number of column vectors included in the precoding matrix is usually the maximum number of beams that the base station can allocate for the terminal device.
  • the number of column vectors included in the precoding matrix is determined by the number of column vectors included in W 2 . Specifically, the number of column vectors included in the precoding matrix is equal to the number of column vectors included in W 2 .
  • the maximum number of terminal device beams is equal to the rank of the channel matrix.
  • the traverse range can be determined according to the rank of the value W 2 channel matrix, i.e., only the number of traverse contained in the column vector is equal to the rank of the channel matrix value W 2, and There is no need to traverse all the values of W 2 , which greatly reduces the amount of calculation. It is not difficult to understand that to adopt this traversal method, the rank of the channel matrix needs to be calculated first.
  • a plurality of methods may be used to calculate the rank of the channel matrix, such as but not limited to Singular Value Decomposition (SVD).
  • the CSI only contains When the feedback period of W 2 arrives but the feedback period of W 1 has not yet arrived, the CSI only contains When the feedback periods of W 1 and W 2 arrive at the same time, the CSI includes both with It is not difficult to understand that when determining the values of W 1 and W 2 for the first time, CSI will also contain with
  • the CSI may further include at least one of the following indications: a Channel Quality Indicator (CQI) and a Rank Indication (RI).
  • CQI Channel Quality Indicator
  • RI Rank Indication
  • the transmitting module 4046 of the terminal device 404 then transmits an uplink symbol 408 to the base station 402 carrying the CSI 4082.
  • the receiving module 4024 of the base station 402 receives the uplink symbol 408 and extracts the CSI 4082 carried therein.
  • the precoding module 4026 of the base station 402 obtains a corresponding precoding matrix according to the CSI 4082 described above.
  • the method of determining the precoding matrix by LTE-Advanced can be referred to to determine the precoding matrix according to CSI 4082.
  • a method of determining a precoding matrix may be when CSI 4082 includes both with The precoding module 4026 is based on with The values of W 1 and W 2 are obtained, and the value of the base codebook W is calculated as a precoding matrix.
  • the values of the matrices W 1 and W 2 vary with time.
  • it may be considered to modify only the values of one of W 1 and W 2 while the other The value remains the same, so the PMI included in CSI 4082 may only be with one of them.
  • the precoding module 4026 needs to store the values of W 1 and W 2 so that the PMI included in the CSI 4082 is only with One of them, the value corresponding to the PMI not included in CSI 4082 can be extended by the previous value.
  • the precoding matrix can be determined by the following method.
  • the PMI carried in the CSI 4082 is extracted and the corresponding value is obtained.
  • the value corresponding to the stored PMI is read; the value corresponding to the PMI carried in the CSI 4082 is The value of the reading is calculated to obtain the value of the base codebook W as a precoding matrix.
  • the stored corresponding value needs to be updated according to the value corresponding to the PMI carried in the CSI 4082.
  • it is used as a precoding matrix. At the same time, in this case, it needs to be based on with The corresponding value updates the stored corresponding value.
  • the precoding module 4026 of the base station 402 can use the precoding matrix to precode the modulation symbols that need to be transmitted to the terminal device 404.
  • the base station precodes the modulation symbols to be transmitted using the precoding matrix.
  • the specific process of precoding can be expressed by the following formula:
  • z k (i) (0 ⁇ k ⁇ p-1) is a pre-coded modulation symbol i
  • the modulation symbol will be transmitted through an antenna port (k);
  • p is the number of antenna ports;
  • y k ( i) (0 ⁇ k ⁇ v-1) is the modulation symbol i on the layer k, which is obtained by layer mapping of the codeword;
  • v is the number of layers ( Equivalent to the number of beams);
  • W is a p ⁇ v-order precoding matrix.
  • layers and antenna ports are used interchangeably. That is to say, for SU-MIMO, the precoding matrix used by the base station can be the same as the precoding matrix reported by the terminal device.
  • the base station needs to calculate a new precoding matrix according to the precoding matrix fed back by the terminal device, for example but not limited to the Zero Forcing algorithm, and then perform according to the new precoding matrix. Precoding operation. Therefore, for MU-MIMO, the precoding matrix W in the above formula (2) should be the above new precoding matrix.
  • the number of column vectors included in the precoding matrix is usually the maximum number of beams that the base station can allocate for the terminal device.
  • the base station may directly perform precoding using the precoding matrix, or extract a partial column vector from the precoding matrix to form a new precoding matrix, and perform precoding according to the new precoding matrix.
  • the base station 402 and the terminal device 404 may include other modules, which are not listed here.
  • the basic codebook is briefly introduced above.
  • the basic codebook is described in more detail below with reference to a specific antenna array.
  • FIG. 5A is an exemplary schematic diagram of an antenna array 500 in accordance with an embodiment of the present invention.
  • the antenna array 500 is a cross-polarized antenna array, and the antenna array specifically includes N 1 ⁇ N 2 cross-polarized antenna pairs 502 arranged in N 1 rows and N 2 columns.
  • Each cross-polarized antenna pair includes two antennas 5022 and 5024, wherein the polarization direction of the antenna 5022 is -45 degrees, and the polarization direction of the antenna 5024 is +45 degrees, so the polarization direction of the antenna 5022 and the pole of the antenna 5024
  • the directions of the turns are 90 degrees apart, that is, the polarization directions of the two antennas are orthogonal to each other.
  • the antennas in the antenna array 500 can be divided into two groups according to the polarization direction.
  • the polarization direction of the first group antenna is -45 degrees, including N 1 ⁇ N 2 antennas, as shown in FIG. 5B; the poles of the second group antennas
  • the direction is +45 degrees and also contains N 1 ⁇ N 2 antennas, as shown in Figure 5C.
  • the antenna array 500 is typically deployed on the side of the base station.
  • the basic codebook W provided by the embodiment of the present invention adopts the dual codebook hierarchical structure introduced in the LTE-Advanced. Specifically, the basic codebook W can be expressed by the following formula:
  • W 1 is a long-term and/or wide-band codebook for characterizing, for example, a channel environment within the entire system bandwidth, the change is relatively slow, and the feedback period can be long.
  • W 2 is a short-term and/or narrow-band codebook for characterizing, for example, the channel environment within a sub-band, the change is relatively fast, and the feedback period needs to be short.
  • W 1 is a block diagonal matrix, which can be expressed as follows:
  • ⁇ is a preset set of N 1 N 2 ⁇ 1 order vectors, which may be orthogonal or non-orthogonal, each vector representing a beam, L being the number of vectors and L ⁇ 2N 1 N 2 .
  • each vector contains N 1 N 2 elements, which respectively correspond to the weights of the N 1 N 2 antennas in the first group antenna or the second group antenna.
  • G is an N 1 N 2 ⁇ M-order matrix, and is used to represent a group of M beams corresponding to the first group of antennas (as shown in FIG. 5B ) in the antenna array 500 , and the vectors corresponding to the M beams are all selected from ⁇ .
  • each vector may be a DFT (Discrete Fourier Transform) vector, or may be a Kronecker product vector. Since there are many selection results for selecting M vectors in ⁇ , G has multiple values.
  • G' is a N 1 N 2 ⁇ M-order matrix, which is used to represent a group of M beams corresponding to the second group of antennas (shown in FIG. 5C ) in the antenna array 500, and the vectors corresponding to the M beams are selected. Since ⁇ . Since there are many selection results for selecting M vectors in ⁇ , G' has multiple values. G and G' may be the same or different.
  • the antennas in the antenna array can be divided into two groups according to specific rules, such as, but not limited to, antenna correlation, and each group includes N 1 N 2 antenna.
  • G and G' can be simply defined as two N 1 N 2 ⁇ M-order matrices, each of which is taken from the same vector group, the vector group containing a plurality of N 1 N 2 ⁇ 1 order vector, each vector represents a beam, and the number of vectors in the vector group is greater than or equal to 2N 1 N 2 .
  • G corresponds to a group of M beams corresponding to a group of antennas in the antenna array
  • G' corresponds to a group of M beams corresponding to another group of antennas in the antenna array.
  • G and G' may be the same or different.
  • the order of G indicates that G corresponds to N 1 N 2 antennas in 2N 1 N 2 , and the position of the N 1 N 2 antennas in the antenna array may or may not be limited; G′ The order indicates that G' corresponds to another N 1 N 2 antennas in 2N 1 N 2 , and the position of the N 1 N 2 antennas in the antenna array may or may not be limited.
  • the number of beams in G may be different from the number of beams in G', and the beams in G and G' may be from the same set of vectors (eg, ⁇ ), or may be from different sets of vectors.
  • the order of vectors in the same group is the same, and the order of vectors between different groups may be the same or different.
  • the number of vectors in each group can be set as needed, for example, it can be set to be greater than or equal to the number of G or G' inner beams, or set to be greater than or equal to the number of antennas in the antenna array.
  • the sum of the number of elements contained in the G inner beam and the number of elements contained in the G' inner beam (that is, the number of lines of W 1 ) is equal to the number of antennas in the antenna array.
  • the number of beams in both G and G' is greater than 1, and the number of beams should not be too large. It can be set according to specific needs (such as the computational complexity associated with the codebook), for example, less than or equal to the number of antennas in the antenna array. .
  • W 1 Since G and G' have multiple values, W 1 has multiple values. Each value of W 1 defines two sets of beams, which are defined by one value of G and one value of G'. Therefore, W 1 can be referred to as a beam matrix or a beam codebook.
  • G corresponds to a group of beams corresponding to the first group of antennas shown in FIG. 5B
  • G′ corresponds to a group of beams corresponding to the second group of antennas shown in FIG. 5C.
  • W 2 can be expressed as follows:
  • ⁇ is the preset cross-polarization leakage value, which is used to characterize the cross-polarized leakage between the polarization direction of the first set of antennas and the polarization direction of the second set of antennas (Cross-Polarized Discrimination, XPD)
  • the degree of influence on the entire antenna array depends on the degree of cross-polarization leakage between the polarization direction of the first set of antennas and the polarization direction of the second set of antennas.
  • ⁇ i and ⁇ i are preset values. It can be seen that ⁇ is a preset set of complex indices.
  • e j ⁇ represents a preset phase rotation factor (co-phasing) for characterizing the phase rotation of the second set of antennas relative to the first set of antennas, wherein ⁇ represents a phase rotation angle.
  • the phase rotation factor can be expressed using ⁇ , and those skilled in the art will appreciate that in addition to ⁇ can be set to e j ⁇ , ⁇ can also take other preset values, the specific value depends on the phase rotation.
  • the design of the matrix B also refers to the cross-polarization leakage value ⁇ , so the cross-polarization factor ⁇ can be used to represent the cross-polarization leakage pair matrix between the polarization direction of the first group antenna and the polarization direction of the second group antenna. The degree of influence of B.
  • ⁇ can also adopt other preset values, and the specific value depends on the phase rotation.
  • the cross polarization factor can adopt a preset value.
  • the matrices A and B are both column vectors. Further, the matrices A and B may be the same or different, and the number of elements other than 0 in the matrices A and B is greater than one.
  • W is a 2N 1 N 2 ⁇ 1 order matrix.
  • GA is an N 1 N 2 ⁇ 1 order matrix, wherein N 1 N 2 elements respectively correspond to weights of N 1 N 2 antennas in the first group of antennas to form a beam through the first group of antennas.
  • GA can be understood as selecting a plurality of beams from a set of M beams (represented by G) corresponding to the first set of antennas through the matrix A, and weight combining the selected beams to form a new one corresponding to the first set of antennas. Beam.
  • the position of the non-zero element in the matrix A in the matrix A determines the position of the selected beam in the matrix G
  • the value of the non-zero element determines the weight of the selected beam.
  • G'B is an N 1 N 2 ⁇ 1 order matrix in which N 1 N 2 elements respectively correspond to weights of N 1 N 2 antennas in the second group of antennas to form a beam through the second group of antennas.
  • G′B can be understood as selecting a plurality of beams from a set of M beams (represented by G′) corresponding to the second group of antennas through the matrix B, and weighting and combining the selected beams to form corresponding to the second group of antennas. A new beam.
  • the position of the non-zero element in the matrix B in the matrix B determines the position of the selected beam in the matrix G'
  • the value of the non-zero element determines the weight of the selected beam.
  • W 2 may be referred to as a weighted combining matrix or a weighted combining codebook, where matrix A is a weighted combining matrix corresponding to the first group of antennas, and matrix B is a weighted combining matrix corresponding to the second group of antennas.
  • W 2 expresses the influence of cross-polarization leakage between the polarization directions of the first group antenna and the second group antenna on the entire antenna array by a preset cross-polarization leakage value and a cross-polarization factor in the matrix B. Degree and extent of impact on the second set of antennas.
  • W 2 represents the phase rotation of the second set of antennas relative to the first set of antennas by the phase rotation factor in matrix B. It should be noted that the above preset values can be set according to specific needs.
  • the value of W 1 can be limited to a limited set, which can be achieved by limiting the size of ⁇ , the number of G values, and/or the number of G' values.
  • the value of W 2 can be limited to a limited set, which can be achieved by limiting the number of values of matrix A and matrix B.
  • the number of values of matrix A can be limited by limiting the number of values of ⁇ i and ⁇ i .
  • matrix B by limiting ⁇ i and The number of values is used to limit the number of values of matrix B.
  • cross-polarization leakage values and cross-polarization factors can be determined after the antenna array is selected, without frequent changes.
  • the number of values of the phase rotation factor can also be limited. By limiting the values of W 1 and W 2 to a limited set, the amount of computation required to determine the precoding matrix can be effectively controlled.
  • elements in matrix A and matrix B may be taken from the same set of preset values, which may be as indicated by elements in ⁇ or ⁇ above.
  • matrix A and matrix B are both column vectors.
  • the number of elements included in the column vector A may be different from the number of elements included in the column vector B. More precisely, the number of elements included in the column vector A is equal to the number of beams in the matrix G, and the number of elements included in the column vector B is equal to the number of beams in the matrix G.
  • the basic codebook provided by the embodiment of the present invention is described in detail above with reference to a cross-polarized antenna array.
  • the description by means of the cross-polarized antenna array is only to more intuitively display the structure of the above basic codebook, and is not intended to limit the application object of the above basic codebook. Therefore, those skilled in the art should understand that the basic codebook provided by the embodiments of the present invention is also applicable to other types of antenna arrays, such as, but not limited to, a close-pack antenna array suitable for a MIMO system as well as a cross-polarized antenna array.
  • a single-polarized antenna array such as shown in FIGS. 5B and 5C
  • a circular antenna array, or the like can also be used.
  • the cross-polar leakage value, the second cross-polarization leakage factor, and/or the phase rotation factor may not be set.
  • the antenna mentioned in the description of the basic codebook process can be understood as a physical antenna, and can also be understood as an antenna port.
  • An antenna port may correspond to one or several physical antennas. When one antenna port corresponds to several physical antennas, a signal transmitted through the antenna port is combined by signals transmitted by several physical antennas.
  • the base station can interact with the terminal device to negotiate a codebook scheme used in the communication process.
  • a radio resource control (RRC) message may be used to indicate the codebook scheme employed.
  • RRC radio resource control
  • the base station indicates that the terminal device uses the existing codebook scheme.
  • the base station indicates that the terminal device uses the codebook solution provided by the embodiment of the present invention.
  • the embodiment of the present invention provides the following codebook structure:
  • W is the basic codebook
  • W 1 is a beam codebook
  • the number of rows is equal to the number of antennas of the base station
  • W 2 is a weighted combined codebook
  • G corresponds to a first set of antennas in the antenna array, and G' corresponds to a second set of antennas in the antenna array;
  • the matrices A and B are column vectors, and the number of non-zero elements included in the column vectors A and B are both greater than 1; the order of the column vector A is equal to the number of column vectors in the matrix G, and the order of the column vector B is equal to the matrix G The number of 'column vectors'.
  • the column vectors in G and G′ may be selected from the same column vector set (the column vector set may also be referred to as a beam set), or may be selected from different column vector sets.
  • the order of the column vectors from the same column vector set is the same, and the order of the column vectors from different column vector sets may be the same or different.
  • the column vectors within the same column vector set may be orthogonal to each other or non-orthogonal.
  • G may correspond to a first group of antennas in the antenna array
  • G′ may correspond to a second group of antennas in the antenna array.
  • the polarization directions of the antennas in each group of antennas are the same, and the polarization directions of the first group antennas may be the same as or different from the polarization directions of the second group antennas.
  • the technical solution provided by the embodiment of the present invention selects multiple beams for each group of antennas to perform weighted combination, thereby constructing a new beam, and weighting the set of antennas by using the new beam.
  • the new beam constructed can more accurately simulate the real environment of the channel and improve the accuracy of precoding.
  • FIG. 6 is an exemplary flow diagram of a CSI feedback method 600 in accordance with an embodiment of the present invention.
  • method 600 can be performed by, for example, but not limited to, a terminal device.
  • Step 602 Receive a downlink symbol from a base station, where the downlink symbol includes a pilot.
  • Step 604 Obtain a channel matrix according to the pilot included in the downlink symbol.
  • Step 606 Calculate a precoding matrix according to the channel matrix and the base codebook.
  • Step 608 Generate CSI according to the precoding matrix.
  • Step 610 Send an uplink symbol to the base station, where the CSI is carried.
  • FIG. 7 is an exemplary flow diagram of a precoding method 700 in accordance with an embodiment of the present invention.
  • method 700 can be performed by, for example, but not limited to, a base station.
  • Step 702 Send a downlink symbol to the terminal device, where the downlink symbol 406 carries a pilot.
  • Step 704 Receive an uplink symbol from a terminal device, and extract a CSI carried therein, where the CSI is generated by the terminal device according to a precoding matrix, where the precoding matrix is generated by the terminal device according to a channel matrix and a base codebook.
  • the channel matrix is generated by the terminal device according to the pilot.
  • Step 706 Generate a precoding matrix according to the CSI.
  • Step 708 Precode the modulation symbols that need to be sent to the terminal device according to the precoding matrix.
  • the precoding matrices used in the precoding process are different under different scenarios, such as SU-MIMO and MU-MIMO.
  • FIG. 8 is a schematic diagram showing the hardware structure of a terminal device 800 according to an embodiment of the invention.
  • the terminal device 800 includes a processor 802, a transceiver 804, a plurality of antennas 806, a memory 808, an I/O (Input/Output) interface 810, and a bus 812.
  • the transceiver 804 further includes a transmitter 8042 and a receiver 8044 that is further configured to store instructions 8082 and data 8084.
  • the processor 802, the transceiver 804, the memory 808, and the I/O interface 810 are communicatively coupled to one another via a bus 812, and the plurality of antennas 806 are coupled to the transceiver 804.
  • the processor 802 can be a general-purpose processor, such as, but not limited to, a central processing unit (CPU), or a dedicated processor such as, but not limited to, a digital signal processor (DSP), an application. ASIC (Application-Specific Integrated Circuit (ASIC) and Field Programmable Gate Array (FPGA). Moreover, processor 802 can also be a combination of multiple processors.
  • the processor 802 is configured to perform, for example, operations performed by the CSI generation module 4044 of the terminal device 404 of FIG. 4, and steps 604-608 of the method 600 of FIG.
  • the processor 802 can be a processor specifically designed to perform the operations and/or steps described above, and can also perform the operations and/or steps described above by reading and executing the instructions 8082 stored in the memory 808. Data 8084 may be required during operation and/or steps.
  • the transceiver 804 includes a transmitter 8042 and a receiver 8044, wherein the transmitter 8042 is configured to transmit an uplink signal to the base station through at least one of the plurality of antennas 806.
  • the receiver 8044 is configured to receive a downlink signal from the base station through at least one of the plurality of antennas 806.
  • Transmitter 8042 is specifically for execution by at least one of a plurality of antennas 806, such as the operations performed by transmit module 4046 of terminal device 404 of FIG. 4, and step 610 of method 600 of FIG.
  • the receiver 8044 is specifically configured to be executed by at least one of the plurality of antennas 806, for example, the operations performed by the receiving module 4042 of the terminal device 404 of FIG. 4, and the step 602 of the method 600 of FIG.
  • the memory 808 can be various types of storage media, such as a random access memory (RAM), a read-only memory (ROM), a non-volatile random access memory (Non-Volatile Random Access Memory, NVRAM), Programmable Read-Only Memory (PROM), Erasable Programmable Read-Only Memory (EPROM), electrically erasable PROM (Electrically Erasable PROM, EEPROM), Flash memory, optical memory, registers, etc.
  • RAM random access memory
  • ROM read-only memory
  • NVRAM non-volatile random access memory
  • PROM Programmable Read-Only Memory
  • EPROM Erasable Programmable Read-Only Memory
  • Electrically erasable PROM Electrically Erasable PROM
  • Flash memory optical memory, registers, etc.
  • the memory 808 is specifically configured to store instructions 8082 and data 8084, and the processor 802 can perform the operations and/or steps described above by reading and executing the instructions 8082 stored in the memory 808, performing the operations and/or
  • the I/O interface 810 is configured to receive instructions and/or data from peripheral devices and to output instructions and/or data to peripheral devices.
  • the terminal device 800 may also include other hardware devices, which are not enumerated herein.
  • FIG. 9 is a schematic diagram showing the hardware structure of a base station 900 according to an embodiment of the invention.
  • base station 900 includes a processor 902, a transceiver 904, a plurality of antennas 906, a memory 908, an I/O interface 910, and a bus 912.
  • the transceiver 904 further includes a transmitter 9042 and a receiver 9044 that is further used to store instructions 9082 and data 9084.
  • the processor 902, the transceiver 904, the memory 908, and the I/O interface 910 are communicatively coupled to one another via a bus 912, and a plurality of antennas 906 are coupled to the transceiver 904.
  • the processor 902 can be a general purpose processor such as, but not limited to, a CPU, or a dedicated processor such as, but not limited to, a DSP, an ASIC, an FPGA, and the like. Moreover, processor 902 can also be a combination of multiple processors.
  • the processor 902 is configured to perform, for example, operations performed by the precoding module 4026 of the base station 402 of FIG. 4, and steps 706-708 of the method 700 of FIG.
  • the processor 902 can be a processor specifically designed to perform the above operations and/or steps, or can be read by
  • the instructions 9082 stored in the memory 908 are fetched and executed to perform the operations and/or steps described above, and the processor 902 may need to use the data 9084 in performing the operations and/or steps described above.
  • the transceiver 904 includes a transmitter 9042 and a receiver 9044, wherein the transmitter 9042 is configured to transmit a downlink signal to the terminal device through at least one of the plurality of antennas 906.
  • the receiver 9044 is configured to receive an uplink signal from the terminal device through at least one of the plurality of antennas 906.
  • Transmitter 9042 is specifically for execution by at least one of a plurality of antennas 906, such as the operations performed by transmit module 4022 of base station 402 of FIG. 4, and step 702 of method 700 of FIG.
  • the receiver 9044 is specifically configured to be executed by at least one of the plurality of antennas 906, for example, the operations performed by the receiving module 4024 of the base station 402 of FIG. 4, and the step 704 of the method 700 of FIG.
  • the memory 908 can be various types of storage media such as RAM, ROM, NVRAM, PROM, EPROM, EEPROM, flash memory, optical memory, and registers, and the like.
  • the memory 908 is specifically configured to store instructions 9082 and data 9084, and the processor 902 can perform the operations and/or steps described above by reading and executing the instructions 9082 stored in the memory 908, performing the operations and/or steps described above.
  • Data 9084 may be required during the process.
  • the I/O interface 910 is for receiving instructions and/or data from peripheral devices and outputting instructions and/or data to peripheral devices.
  • the base station 900 may also include other hardware devices, which are not enumerated herein.

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Abstract

本发明实施例提供了一种信道状态信息CSI反馈方法，包括接收来自基站的下行符号，其中，该下行符号中包含导频；根据该下行符号中包含的导频获得信道矩阵；根据该信道矩阵和基础码本计算预编码矩阵；根据该预编码矩阵生成CSI；向基站发送上行符号，其中，所述上行符号中携带所述CSI。此外本发明实施例还提供了一种预编码方法、终端设备和基站。本发明实施例提供的技术方案为每一组天线选择至少一个波束进行加权合并，以此来构造一个新的波束，并使用这个新的波束对这组天线进行加权。所构造的新的波束可以更加精准的模拟信道真实环境，提升预编码的精确度。

Description

信道状态信息反馈方法、预编码方法、终端设备和基站
本申请要求于2016年5月12日提交中国专利局、申请号为201610316773.X、发明名称为“信道状态信息反馈方法、预编码方法、终端设备和基站”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本发明涉及多天线技术，尤其涉及一种信道状态信息反馈方法、预编码方法、终端设备和基站。
背景技术
多入多出(Multiple Input Multiple Output，MIMO)技术的出现，给无线通信带来了革命性的变化。通过在发射端设备和接收端设备上同时部署多根天线，MIMO技术可以同时提供彼此独立的多个信道，数据传输速率因而得到成倍的提升。
图1是MIMO的应用场景示意图。图1示出的应用场景包括发射端设备102和接收端设备104。其中，发射端设备102可以是例如但不限于基站。接收端设备104可以是例如但不限于终端设备。发射端设备102配置有n(n>1)根发射天线，具体表示为发射天线1～n。接收端设备104配置有m(m>1)根接收天线，具体表示为接收天线1～m。如此一来，上述n根发射天线和m根接收天线之间共存在m×n个信道，如发射天线1～n与接收天线1～m之间的实线所示(部分信道未示出)。
在理想情况下(例如不考虑噪声)，上述m×n个信道可通过如下信道矩阵来表示：
Figure PCTCN2017079346-appb-000001
其中，hij(1≤i≤m,1≤j≤n)表示发射天线j与接收天线i之间的信道的信道增益。接收端设备104可通过发射端设备102发射的导频(Pilot)来确定上述信道矩阵。
如图2所示，上述m×n个信道可以等效为彼此独立的i个信道。这些信道又称为波束(Beam)，可以通过多种技术获得，例如预编码(Precoding)技术。预编码技术通过预编码矩阵(Precoding Matrix)来定义波束。具体来说，预编码矩阵的每个列向量(也称为预编码向量，Precoding Vector)对应一个波束。列向量的元素与天线(或者天线端口(Antenna Port))一一对应， 用于对天线进行加权，从而使天线发射的信号相互叠加形成波束。终端设备波束的最大数量等于信道矩阵的奇异值的数量，即信道矩阵的秩(Rank)。当部分奇异值过小(低于预设阈值)时，还可以从上述数量中减去数值过小的奇异值的数量。为便于描述，本文统一以信道矩阵的秩来表示上述彼此独立的信道的数量。
预编码技术使用预设的码本来记录预编码矩阵。接收端设备104根据上述信道矩阵，基于预设的选择标准(例如但不限于最大信道容量准则、最小均方误差准则或者最小奇异值准则等)，在码本中选择合适的码字来表示预编码矩阵，其中，每种选择标准有多种算法可供选择。
现有码本是针对视距(Line Of Sight，LOS)信道设计的，然而实际信道往往多为非视距(Non Line of Sight，NLOS)信道。因此基于LOS码本来确定NLOS信道的预编码矩阵，精确十分有限。
发明内容
有鉴于此，实有必要提供一种信道状态信息CSI反馈方法，提高现有预编码矩阵的精确度。
同时，提供一种预编码方法，提高现有预编码矩阵的精确度。
同时，提供一种终端设备，提高现有预编码矩阵的精确度。
同时，提供一种基站，提高现有预编码矩阵的精确度。
依照本发明的第一方面，提供一种信道状态信息CSI反馈方法，包括：
接收来自基站的下行符号，其中，该下行符号中包含导频；
根据该下行符号中包含的导频获得信道矩阵；
根据该信道矩阵和基础码本计算预编码矩阵；
根据该预编码矩阵生成CSI；
向基站发送上行符号，其中，所述上行符号中携带所述CSI。
依照本发明的第二方面，提供一种预编码方法，包括：
向终端设备发送下行符号，该下行符号中携带导频；
接收来自终端设备的上行符号，提取其中携带的信道状态信息CSI，其中，所述CSI由所述终端设备根据预编码矩阵生成，该预编码矩阵由所述终端设备根据信道矩阵和基础码本生成，该信道矩阵由所述终端设备根据所述导频生成；
根据所述CSI生成预编码矩阵；
根据所述预编码矩阵对需要发送给终端设备的调制符号进行预编码。
依照本发明的第三方面，提供一种终端设备，包括：
接收模块，用于接收来自基站的下行符号；
信道状态信息CSI生成模块，用于根据该下行符号中包含的导频获得信道矩阵，根据该信道矩阵和基础码本计算预编码矩阵，根据该预编码矩阵生成CSI；
发射模块，用于向基站发送上行符号，其中，所述上行符号中携带所述CSI。
依照本发明的第四方面，提供一种基站，包括：
发射模块，用于向终端设备发送下行符号，该下行符号中携带导频；
接收模块，用于接收来自终端设备的信道状态信息CSI，其中，所述CSI由所述终端设备根据预编码矩阵生成，该预编码矩阵由所述终端设备根据信道矩阵和基础码本生成，该信道矩阵由所述终端设备根据所述导频生成；
预编码模块，用于根据所述CSI生成预编码矩阵，以及根据所述预编码矩阵对需要发送给终端设备的调制符号进行预编码。
在上述各个方面中，其中，所述基站配置有天线阵列，所述基础码本为：
W＝W1W2
其中W为所述基础码本，W1为波束码本，其行数等于基站的天线数量，W2为加权合并码本；
Figure PCTCN2017079346-appb-000002
G与天线阵列之中的第一组天线相对应，G′与天线阵列之中的第二组天线相对应；
Figure PCTCN2017079346-appb-000003
矩阵A和B均为列向量，且列向量A和B中包含的非零元素数量均大于1；列向量A所包含的元素的数量等于矩阵G中列向量的数量，列向量B所包含的元素的数量等于矩阵G′中列向量的数量。
可选的，所述天线阵列中包含2N1N2根天线，第一组天线和第二组天线均包含N1N2根天线，且
Figure PCTCN2017079346-appb-000004
Figure PCTCN2017079346-appb-000005
Ω为预设的一组N1N2×1阶向量，这些向量彼此正交或者非正交，L是向量的数量并且L≥2N1N2；G中的列向量彼此正交或者非正交；G′中的列向量彼此正交或者非正交；
Figure PCTCN2017079346-appb-000006
其中τ为第二组天线的极化方向与第一组天线的极化方向之间的交叉极化泄漏的值；
Figure PCTCN2017079346-appb-000007
Figure PCTCN2017079346-appb-000008
其中，λi和φi为预设值，
Figure PCTCN2017079346-appb-000009
Figure PCTCN2017079346-appb-000010
Figure PCTCN2017079346-appb-000011
其中θ为第二组天线相对于第一组天线的相位旋转角度，γi和
Figure PCTCN2017079346-appb-000012
为预设值，
Figure PCTCN2017079346-appb-000013
可选的，G与G′相同或者不同；A与B相同或者不同。
可选的，G和G′中的列向量可以选自同一个列向量集合，也可以选自不同的列向量集合。来自同一列向量集合的列向量的阶数相同，来自不同列向量集合的列向量的阶数可以相同也可以不同。
可选的，每组天线内各天线的极化方向相同，第一组天线的极化方向与第二组天线的极化方向可以相同也可以不同。
本发明实施例提供的技术方案为每一组天线选择多个波束进行加权合并，以此来构造一个新的波束，并使用这个新的波束对这组天线进行加权。所构造的新的波束可以更加精准的模拟信道真实环境，提升预编码的精确度。
附图说明
图1是MIMO的应用场景示意图；
图2是MIMO等效信道示意图；
图3是依照本发明一实施例的无线通信网络的示范性示意图；
图4是依照本发明一实施例的CSI反馈过程示意图；
图5A是依照本发明一实施例的天线阵列的示范性示意图；
图5B是图5A所示天线阵列中第一组天线的示范性示意图；
图5C是图5A所示天线阵列中第二组天线的示范性示意图；
图6是依照本发明一实施例的CSI反馈方法的示范性流程图
图7是依照本发明一实施例的预编码方法的示范性流程图。
图8是依照本发明一实施例的终端设备的硬件结构示意图。
图9是依照本发明一实施例的基站的硬件结构示意图。
具体实施方式
伴随着通信理论和实践的不断发展，越来越多的无线通信技术开始出现并且逐步走向成熟。上述无线通信技术包括但不限于时分多址(Time Division Multiple Access，TDMA)技术、频分多址(Frequency Division Multiple Access，FDMA)技术、码分多址(Code Division Multiple Access，CDMA)技术、时分同步码分多址(Time Division-Synchronous Code Division Multiple Access，TD-SCDMA)、正交频分多址(Orthogonal FDMA，OFDMA)技术、单载波频分多址(Single Carrier FDMA，SC-FDMA)技术、空分多址(Space Division Multiple Access，SDMA)技术以及这些技术的演进及衍生技术等。上述无线通信技术作为无线接入技术(Radio Access Technology，RAT)被众多无线通信标准所采纳，从而构建出了在今天广为人们所熟知的各种无线通信系统(或者网络)，包括但不限于全球移动通信系统(Global System for Mobile Communications，GSM)、CDMA2000、宽带CDMA(Wideband CDMA，WCDMA)、由802.11系列标准中定义的WiFi、全球互通微波存取(Worldwide Interoperability for Microwave Access，WiMAX)、长期演进(Long Term Evolution，LTE)、LTE升级版(LTE-Advanced，LTE-A)以及这些无线通信系统的演进系统等。如无特别说明，本发明实施例提供的技术方案可应用于上述各种无线通信技术和无线通信系统。此外，术语“系统”和“网络”可以相互替换。
图3是依照本发明一实施例的无线通信网络300的示范性示意图。如图3所示，无线通信网络300包括基站302～306和终端设备308～322，其中，基站302～306彼此之间可通过回程(backhaul)链路(如基站302～306之间的直线所示)进行通信，该回程链路可以是有线回程链路(例如光纤、铜缆)，也可以是无线回程链路(例如微波)。终端设备308～322可通过无线链路(如基站302～306与终端设备308～322之间的折线所示)与基站302～306通信。
基站302～306用于为终端设备308～318提供无线接入服务。具体来说，每个基站都提供一个服务覆盖区域(又可称为蜂窝，如图3中各椭圆区域所示)，进入该区域的终端设备可通过无线信号与基站通信，以此来接受基站提供的无线接入服务。基站的服务覆盖区域之间可能存在交叠，处于交叠区域内的终端设备可收到来自多个基站的无线信号。例如，如图3所示，基站302与基站304的服务覆盖区域存在交叠，终端设备312便处于该交叠区域之内，因此终端设备312可以收到来自基站302和基站304的无线信号。又例如，如图3所示，基站302、304和306的服务覆盖区域存在一个共同的交叠区域，终端设备320便处于该交叠区域之内，因此终端设备320可以收到来自基站302、304和306的无线信号。
依赖于所使用的无线通信技术，基站又可称为节点B(NodeB)，演进节点B(evolved NodeB,eNodeB)以及接入点(Access Point，AP)等。此外，根据所提供的服务覆盖区域的大小，基站又可分为用于提供宏蜂窝(Macro  cell)的宏基站、用于提供微蜂窝(Pico cell)的微基站和用于提供毫微微蜂窝(Femto cell)的毫微微基站。随着无线通信技术的不断演进，未来的基站也可以采用其他的名称。
终端设备308～318可以是具备无线通信功能的各种无线通信设备，例如但不限于移动蜂窝电话、无绳电话、个人数字助理(Personal Digital Assistant，PDA)、智能电话、笔记本电脑、平板电脑、无线数据卡、无线调制解调器(Modulator demodulator，Modem)或者可穿戴设备如智能手表等。随着物联网(Internet of Things，IOT)技术的兴起，越来越多之前不具备通信功能的设备，例如但不限于，家用电器、交通工具、工具设备、服务设备和服务设施，开始通过配置无线通信单元来获得无线通信功能，从而可以接入无线通信网络，接受远程控制。此类设备因配置有无线通信单元而具备无线通信功能，因此也属于无线通信设备的范畴。此外，终端设备308～318还可以称为移动台、移动设备、移动终端、无线终端、手持设备、客户端等。
基站302～306，和终端设备308～322均可配置有多根天线，以支持MIMO技术。进一步的说，终端设备308～322既可以支持单用户MIMO(Single-User MIMO，SU-MIMO)，还可以借助SDMA技术支持多用户MIMO(Multi-User MIMO，MU-MIMO)。由于配置有多根天线，基站302～306和终端设备308～322还可灵活支持单入单出(Single Input Single Output，SISO)技术、单入多出(Single Input Multiple Output，SIMO)和多入单出(Multiple Input Single Output，MISO)技术，其中SIMO又称为接收分集(Receive Diversity，RD)，MISO又称为发射分集(Transmit Diversity，TD)。
此外，基站302与终端设备304～310可采用各种无线通信技术进行通信，例如但不限于上文提到的各种无线通信技术。
应注意，图3所示的无线通信网络300仅用于举例，并非用于限制本发明的技术方案。本领域的技术人员应当明白，在具体实现过程中，无线通信网络300还包括其他设备，例如但不限于基站控制器(Base Station Controller，BSC)，同时也可根据具体需要来配置基站和终端设备。
依照本发明实施例提供的技术方案，终端设备向基站反馈信道状态信息(Channel State Information，CSI)，基站根据该CSI对需要发给终端设备的无线信号进行调整，以便在终端设备一侧实现更好的接收效果。下面就对本发明实施例提供的CSI反馈过程进行具体描述。
图4是依照本发明一实施例的CSI反馈过程示意图。CSI反馈过程在基站402与终端设备404之间进行。如图4所示，基站402具体包括发射模块4022、接收模块4024和预编码模块4026。终端设备404具体包括接收模块4042、CSI生成模块4044和发射模块4046。CSI反馈的具体过程如下文所述。
基站402的发射模块4022发送下行符号406，该下行符号406中携带导频4062。具体来说，下行符号406可以为，例如但不限于，正交频分复用(Orthogonal frequency-division multiplexing，OFDM)符号。OFDM符号通常通过对一组子载波(Sub-Carrier)进行加权求和来获得，子载波的权重为 待发送的调制符号(一般为复数)，其中包括导频。
终端设备404的接收模块4024接收上述下行符号406。
终端设备404的CSI生成模块4044根据下行符号406中包含的导频4062获得信道矩阵。
此后，CSI生成模块4044根据上述信道矩阵和基础码本确定合适的预编码矩阵，并根据该预编码矩阵生成CSI。
本发明实施例提供的基础码本与LTE-Advanced中的码本相似，都采用两级码本结构，一级为长期和/或宽带码本W1，二级为短期和/或窄带码本W2。W1和W2均为矩阵且二者均有多个取值。基础码本W为矩阵W1与W2的乘积，因此基础码本W也是矩阵且也有多个取值，每个取值都是一个预编码矩阵。本发明实施例提供的基础码本W将在下文结合图5A～5C进行更为详细的描述。
由于基础码本与LTE-Advanced中的码本相似，因此可参考LTE-Advanced确定预编码矩阵的方法，来根据信道矩阵和基础码本确定预编码矩阵。下文列举几种常用方法，来说明预编码矩阵的确定过程。本领域的技术人员应当明白，这些方法仅仅用作举例，并非用于限制本发明的范围，在具体实现过程中，还可以使用其他方法来确定预编码矩阵。
常用的一种确定预编码矩阵的方法是，遍历矩阵W1和W2的所有取值以获得W1和W2的所有组合，据此计算得到基础码本W的所有取值，再根据信道矩阵从基础码本W的所有取值中选择符合预设选择标准的预编码矩阵，并将该预编码矩阵对应的W1和W2的取值所对应的索引，携带在对应的预编码矩阵指示(PM Indicator，PMI)中，作为CSI反馈。具体来说，可通过
Figure PCTCN2017079346-appb-000014
来携带W1的取值的索引，通过
Figure PCTCN2017079346-appb-000015
来携带W2的取值的索引。
另一方面，矩阵W1和W2的取值随时间的变化情况不尽相同，其中，W1的取值变化相对缓慢，W2的取值变化相对较快。如此一来，在确定预编码矩阵时，可以考虑仅仅修改W1和W2其中一个的取值，而另一个的取值保持不变，这样一来不仅可以大大降低预编码矩阵的计算量，同时也可以降低CSI反馈开销。不难理解，实现上述方案的前提，是W1和W2的变化周期不同，因此，可以为W1和W2规定不同的反馈周期，例如，由于W1的取值变化较慢，可以为W1设置较长的反馈周期；W2的取值变化较快，可以为W2设置较短的反馈周期。同时，为了在修改W1和W2其中一个矩阵的取值的同时，另一个矩阵的取值可以延用之前的取值，还需要对W1和W2的取值进行存储。W1和W2的最初取值，可以依照前一种方法获得，也可以使用缺省取值。在存储过程中，既可以存储具体的取值，也可以存储取值对应的索引。下文仅以存储具体的取值为例进行描述，但是本领域的技术人员应当明白，下列描述同样适用于存储取值对应的索引的情况。
在一些情况下，若W1发生变化，W2也必然发生变化，也就是说，在到达W1的反馈周期时，需要采用上述遍历矩阵W1和W2的所有取值的方式来确定预编码矩阵。
在此基础上，可以参照如下方法确定预编码矩阵。在W1和W2其中一个矩阵的反馈周期到达时，可以遍历该矩阵的所有取值，并将其与所存储的、反馈周期尚未到达的矩阵的取值一一组合，计算得到基础码本W的所有取值，再根据信道矩阵从这些取值中选择符合预设选择标准的预编码矩阵，并将该预编码矩阵对应的、反馈周期已到达的矩阵的取值所对应的索引，携带在对应的PMI中，作为CSI反馈。同时，还需要使用预编码矩阵对应的、反馈周期已到达的矩阵的取值，对存储的对应取值进行更新。不难理解，在这种方法中，如果W1和W2的反馈周期同时到达，则可以使用前一种方法确定W1和W2的取值，并携带在对应的PMI中，作为CSI反馈，同时还需要使用这些取值对存储的对应取值进行更新。
如上文所述，预编码矩阵的每一个列向量对应一个波束，因此预编码矩阵所包含的列向量的数量通常就是基站可以为终端设备分配的波束的最大数量。预编码矩阵所包含列向量的数量是由W2所包含列向量的数量决定的，具体来说，预编码矩阵所包含列向量的数量等于W2所包含列向量的数量。另一方面，如上文所述，终端设备波束的最大数量等于信道矩阵的秩。如此一来，在确定预编码矩阵的过程中，可根据信道矩阵的秩来确定W2取值的遍历范围，即仅遍历所包含列向量数量等于信道矩阵的秩的W2的取值，而无需遍历W2的所有取值，从而大大降低计算量。不难理解，若要采用这种遍历方法，需要首先计算信道矩阵的秩。在具体实现过程中，可采用多种方法计算信道矩阵的秩，例如但不限于奇异值分解(Singular Value Decomposition，SVD)等。
结合上文所述可知，当W1的反馈周期到达但W2的反馈周期尚未到达时，CSI仅仅包含
Figure PCTCN2017079346-appb-000016
当W2的反馈周期到达但W1的反馈周期尚未到达时，CSI仅仅包含
Figure PCTCN2017079346-appb-000017
当W1和W2的反馈周期同时到达时，CSI同时包含
Figure PCTCN2017079346-appb-000018
和
Figure PCTCN2017079346-appb-000019
不难理解，在首次确定W1和W2的取值时，CSI也会同时包含
Figure PCTCN2017079346-appb-000020
和
Figure PCTCN2017079346-appb-000021
除了包含PMI，上述CSI还可包括下列指示之中的至少一种：信道质量指示(Channel Quality Indicator，CQI)和秩指示(Rank Indication，RI)。
上述基础码本的具体结构将在下文进行更为详细的描述。
终端设备404的发送模块4046随后向基站402发送上行符号408，其中携带CSI 4082。
基站402的接收模块4024接收上述上行符号408，提取其中携带的CSI4082。
基站402的预编码模块4026根据上述CSI 4082，获得对应的预编码矩阵。
由于基础码本与LTE-Advanced中的码本相似，因此可参考LTE-Advanced确定预编码矩阵的方法，来根据CSI 4082确定预编码矩阵。具体来说，一种确定预编码矩阵的方法可以是，当CSI 4082同时包含
Figure PCTCN2017079346-appb-000022
和
Figure PCTCN2017079346-appb-000023
时，预编码模块4026根据
Figure PCTCN2017079346-appb-000024
和
Figure PCTCN2017079346-appb-000025
获得W1和W2的取值，据此计算得到基础码本W的取值，作为预编码矩阵。
此外，如上文所述，矩阵W1和W2的取值随时间的变化情况不尽相同，在确定预编码矩阵时，可以考虑仅仅修改W1和W2其中一个的取值，而另一个的取值保持不变，因此CSI 4082所包含的PMI可能仅为
Figure PCTCN2017079346-appb-000026
和
Figure PCTCN2017079346-appb-000027
其中之一。在这种情况下，预编码模块4026需要对W1和W2的取值进行存储，以便在CSI 4082所包含的PMI仅为
Figure PCTCN2017079346-appb-000028
和
Figure PCTCN2017079346-appb-000029
其中之一，CSI 4082未包含的PMI所对应的取值可以延用之前的取值。在存储过程中，既可以存储具体的取值，也可以存储取值对应的索引。下文仅以存储具体的取值为例进行描述，但是本领域的技术人员应当明白，下列描述同样适用于存储取值对应的索引的情况。
在此基础上，可以采用如下方法确定预编码矩阵。提取CSI 4082中携带的PMI并获取其对应的取值；对于CSI 4082中未携带的PMI，读取所存储的该PMI所对应的取值；依据CSI 4082中携带的PMI所对应的取值和读取的取值计算得到基础码本W的取值，作为预编码矩阵。应注意，在这种情况下，需要根据CSI 4082中携带的PMI所对应的取值对存储的对应取值进行更新。此外，当CSI 4082中同时携带
Figure PCTCN2017079346-appb-000030
和
Figure PCTCN2017079346-appb-000031
时，可根据前一种方法计算得到基础码本W的取值，作为预编码矩阵。同时，在这种情况下，需要根据
Figure PCTCN2017079346-appb-000032
和
Figure PCTCN2017079346-appb-000033
所对应的取值对存储的对应取值进行更新。
在获得预编码矩阵之后，基站402的预编码模块4026便可使用该预编码矩阵对需要发送给终端设备404的调制符号进行预编码。
基站使用预编码矩阵对待发送的调制符号进行预编码。例如，对于SU-MIMO而言，预编码的具体过程可通过如下公式表示：
Figure PCTCN2017079346-appb-000034
其中，zk(i)(0≤k≤p-1)为经过预编码得到的调制符号i，该调制符号将通过天线端口(Antenna Port)k发送；p为天线端口的数量；yk(i)(0≤k≤v-1)为层(Layer)k上的调制符号i，该调制符号是通过对码字(codeword)进行层映射(Layer Mapping)而得到的；v为层数(等同于波束数量)；W为p×v阶预编码矩阵。在本文中，层与天线端口可互换使用。也就是说，对于SU-MIMO而言，基站所使用的预编码矩阵可以与终端设备上报的预编码矩阵相同。然而，对于MU-MIMO而言，基站需要根据终端设备反馈的预编码矩阵，通过，例如但不限于迫零(Zero Forcing)算法，计算一个新的预编码矩阵，然后依照新的预编码矩阵执行预编码操作。因此，对于MU-MIMO而言，上述公式(2)中的预编码矩阵W应为上述新的预编码矩阵。
如上文所述，预编码矩阵所包含的列向量的数量通常就是基站可以为终端设备分配的波束的最大数量。基站可以直接使用预编码矩阵进行预编码，也可以从预编码矩阵中抽取部分列向量构成新的预编码矩阵，并根据新的预编码矩阵进行预编码。
应注意，本领域的技术人员应当明白，在具体实现过程中，基站402和终端设备404均可包括其他模块，在此不再一一列出。
上文对基础码本进行了简要的介绍，下文结合具体的天线阵列对基础码本进行更为详细的介绍。
图5A是依照本发明一实施例的天线阵列500的示范性示意图。如图5A所示，天线阵列500为一交叉极化天线阵列，该天线阵列具体包含排列成排列成N1行N2列的N1×N2个交叉极化天线对502。每个交叉极化天线对包含两根天线5022和5024，其中天线5022的极化方向是-45度，天线5024的极化方向是+45度，因此天线5022的极化方向与天线5024的极化方向相差90度，也就是说，这两根天线的极化方向彼此正交。天线阵列500中的天线可以按照极化方向分为两组，第一组天线的极化方向为-45度，包含N1×N2根天线，如图5B所示；第二组天线的极化方向为+45度，同样包含N1×N2根天线，如图5C所示。天线阵列500通常部署在基站一侧。
下面就结合图5所示的天线阵列500对本发明实施例提供的基础码本进行详细介绍。
本发明实施例提供的基础码本W，采用LTE-Advanced中引入的双码本层次化结构，具体来说，该基础码本W可通过如下公式表示：
W＝W1W2          (3)
其中，W1为长期和/或宽带码本，用于表征例如整个系统带宽内的信道环境，变化相对缓慢，反馈周期可以很长。W2为短期和/或窄带码本，用于表征例如子带内的信道环境，变化相对较快，反馈周期需要很短。
W1为块对角矩阵，具体可表示如下：
Figure PCTCN2017079346-appb-000035
其中，
Figure PCTCN2017079346-appb-000036
Figure PCTCN2017079346-appb-000037
Ω为预设的一组N1N2×1阶向量，这些向量可以正交也可以非正交，每个向量代表一个波束，L是向量的数量并且L≥2N1N2。此外，每个向量包含N1N2个元素，分别对应第一组天线或者第二组天线中的N1N2根天线的权重。G为N1N2×M阶矩阵，用于表示天线阵列500中第一组天线(如图5B所示)对应的一组M个波束，这M个波束对应的向量均选自Ω。在具体实现过程中，每个向量可以是DFT(Discrete Fourier Transform，离散傅里叶变换)向量，也可以是克罗内克积(Kronecker product)向量。由于在Ω中选择M个向量的 选择结果有很多种，因此G有多个取值。同理，G′为N1N2×M阶矩阵，用于表示天线阵列500中第二组天线(如图5C所示)对应的一组M个波束，这M个波束对应的向量均选自Ω。由于在Ω中选择M个向量的选择结果有很多种，因此G′有多个取值。G和G′可以相同也可以不同。
通常来说，对于包含2N1N2根天线的天线阵列，可以依照特定规则，例如但不限于，天线相关性，将该天线阵列中的天线分为两组，每组包含N1N2根天线。在这种情况下，可将G和G′简单定义为两个N1N2×M阶矩阵，这两个矩阵的每个列向量均取自同一个向量组，该向量组包含多个N1N2×1阶向量，每个向量代表一个波束，且向量组中向量的数量大于等于2N1N2。不难看出，G对应天线阵列中一组天线对应的一组M个波束，G′对应天线阵列中另一组天线对应的一组M个波束。G和G′可以相同也可以不同。此外，本领域的技术人员应当明白，也可无需对上述2N1N2根天线进行分组，例如但不限于，当天线阵列采用密排天线阵列的情况下。不难看出，G的阶数表明G对应2N1N2中的N1N2根天线，可以对这N1N2根天线在天线阵列中的位置进行限定，也可以不做限定；G′的阶数表明G′对应2N1N2中的另外N1N2根天线，可以对这N1N2根天线在天线阵列中的位置进行限定也可以不做限定。更进一步的，G中波束的数量可以不同于G′中波束的数量，且G和G′中的波束可以来自同一组向量(例如Ω)，也可以来自不同的两组向量。相同组内向量的阶数相同，不同组之间向量的阶数可以相同也可以不同。每组内向量的数量可根据需要进行设置，例如可设置为大于等于所对应的G或者G′内波束的数量，也可设置为大于等于天线阵列中天线的数量。G内波束中包含的元素数量与G′内波束中包含的元素数量之和(也就是W1的行数)等于天线阵列中天线的数量。G和G′中波束的数量均大于1，且波束的数量均不应过大，可根据具体需要(例如与码本有关的运算复杂度)进行设置，例如均小于等于天线阵列中的天线数量。
由于G和G′均有多个取值，W1也就有多个取值。W1的每个取值定义了两组波束，分别由G的一个取值和G′的一个取值来定义。因此W1可称为波束矩阵或者波束码本。例如，G对应图5B所示的第一组天线所对应的一组波束，G′对应图5C所示的第二组天线所对应的一组波束。
W2具体可表示如下：
Figure PCTCN2017079346-appb-000038
其中，
Figure PCTCN2017079346-appb-000039
代表归一化系数，τ是预设交叉极化泄漏值，用于表征第一组天线的极化方向与第二组天线的极化方向之间的交叉极化泄漏(Cross-Polarized Discrimination，XPD)对整个天线阵列的影响程度，其具体的取值取决于第一组天线的极化方向与第二组天线的极化方向之间的交叉极化泄漏的程度。
同时：
Figure PCTCN2017079346-appb-000040
其中：
Figure PCTCN2017079346-appb-000041
λi和φi为预设值。可见δ为预设的一组复指数。
同时：
Figure PCTCN2017079346-appb-000042
其中，ejθ代表预设的相位旋转因子(co-phasing)，用于表征第二组天线相对于第一组天线的相位旋转情况，其中θ代表相位旋转角度。相位旋转因子可以使用ε来表示，本领域的技术人员应当明白，除了可以将ε设置为ejθ之外，ε还可以采用其他的预设取值，具体的取值取决相位旋转的情况。此外，矩阵B的设计也参考了交叉极化泄漏值τ，因此可用交叉极化因子μ表示第一组天线的极化方向与第二组天线的极化方向之间的交叉极化泄漏对矩阵B的影响程度。本领域的技术人员应当明白，除了可以将μ设置为τ之外，μ还可以采用其他的预设取值，具体的取值取决相位旋转的情况。在具体实现过程中，交叉极化因子可采用预设值。
Figure PCTCN2017079346-appb-000043
其中γi和
Figure PCTCN2017079346-appb-000044
为预设值。可见上述σ为预设的一组复指数。
由此可见，矩阵A和B均为列向量。此外，矩阵A和B可以相同也可以不同，且矩阵A和B中不为0的元素的数量均大于1。
同时，对于矩阵A而言：
Figure PCTCN2017079346-appb-000045
同时，对于矩阵B而言：
Figure PCTCN2017079346-appb-000046
依照上述定义可知：
Figure PCTCN2017079346-appb-000047
因此，W为2N1N2×1阶矩阵。其中，GA为N1N2×1阶矩阵，其中的N1N2个元素分别对应第一组天线中的N1N2根天线的权重，以便通过第一组天线形成波束。GA可以理解为通过矩阵A在第一组天线对应的一组M个波束(由G表示)中选择多个波束，并对选中的波束进行加权合并，形成对应于第一组天线的一个新的波束。其中，矩阵A中的非零元素在矩阵A中的位置决定了矩阵G中被选中的波束的位置，该非零元素的值决定了该被选中波束的权重。G′B为N1N2×1阶矩阵，其中的N1N2个元素分别对应第二组天线中的N1N2根天线的权重，以便通过第二组天线形成波束。G′B可以理解为通过矩阵B在第二组天线对应的一组M个波束(由G′表示)中选择多个波束，并对选中的波束进行加权合并，形成对应于第二组天线的一个新的波束。其中，矩阵B中的非零元素在矩阵B中的位置决定了矩阵G′中被选中的波束的位置，该非零元素的值决定了该被选中波束的权重。因此，W2可称为加权合并矩阵或者加权合并码本，其中矩阵A为第一组天线对应的加权合并矩阵，矩阵B为第二组天线对应的加权合并矩阵。此外，W2通过预设的交叉极化泄漏值和矩阵B中的交叉极化因子来表现第一组天线与第二组天线的极化方向之间的交叉极化泄漏对整个天线阵列的影响程度和对第二组天线的影响程度。同时，W2通过矩阵B中的相位旋转因子来表现第二组天线相对于第一组天线的相位旋转。应注意，上述预设值均可以根据具体需要进行设置。
上文对矩阵W1和W2的构成进行了描述。在具体实现过程中，可将W1的取值限定在一个有限的集合之内，这可以通过限制Ω的大小、G取值的数量和/或G′取值的数量来实现。同理，可将W2的取值限定在一个有限的集合之内，这可以通过限制矩阵A和矩阵B取值的数量来实现。例如，对于矩阵A而言，可通过限制λi和φi取值的数量，来限制矩阵A的取值数量。同理，对于矩阵B而言，可通过限制γi和
Figure PCTCN2017079346-appb-000048
取值的数量，来限制矩阵B的取值数量。此外，在天线阵列选定之后，交叉极化泄漏值和交叉极化因子也可随之确定，无需频繁更改。同时，也可限制相位旋转因子的取值的数量。通过将W1和W2的取值各自限定在有限的集合之内，可有效控制确定预编码矩阵带来的运算量。
在如上文所述的W2的结构中，矩阵A和矩阵B中的元素可以取自同一组预设值，这组预设值可以如上文δ或者σ中的元素所示。如上文所述，矩阵A和矩阵B均为列向量。列向量A所包含的元素的数量可以不同于列向量B所包含的元素的数量。更为准确的说，列向量A所包含的元素的数量等于矩阵G中波束的数量，列向量B所包含的元素的数量等于矩阵G中波束的数量。
在选定W1和W2之后，可分别通过
Figure PCTCN2017079346-appb-000049
和
Figure PCTCN2017079346-appb-000050
来反馈选定的W1和W2，其中，
Figure PCTCN2017079346-appb-000051
的反馈周期大于
Figure PCTCN2017079346-appb-000052
的反馈周期，因此
Figure PCTCN2017079346-appb-000053
的反馈频率低于
Figure PCTCN2017079346-appb-000054
的反馈频率。
上文参考交叉极化天线阵列对本发明实施例提供的基础码本进行了详细的描述。然而，本领域的技术人员应当明白，借助交叉极化天线阵列进行描述的目的仅仅是更为直观的展现上述基础码本的结构，而并非用于限制上述基础码本的应用对象。因此，本领域的技术人员应当明白，本发明实施例提供的基础码本同样适用于其他类型的天线阵列，例如但不限于，与交叉极化天线阵列同样适用于MIMO系统的密排天线阵列。此外，还可以使用单极化天线阵列(例如图5B和图5C所示)，圆形天线阵列等。当采用其他类型的天线阵列时，上述交叉极化泄漏值、第二交叉极化泄漏因子和/或相位旋转因子可不再设置。
同时，描述基础码本过程中提到的天线，即可理解为物理天线，也可理解为天线端口。一个天线端口可对应一根或者几根物理天线，当一个天线端口对应几根物理天线时，通过该天线端口发射的信号由几根物理天线发射的信号组合而成。
如上文所述，本发明实施例提供的技术方案对现有二级码本进行了改进。在具体实现过程中，基站可以与终端设备交互，以协商通信过程中使用的码本方案。例如，可借助无线资源控制(Radio Resource Control，RRC)消息来指示所采用的码本方案。当基站发往终端设备的RRC消息中携带现有码本方案的指示时，说明基站指示终端设备使用现有码本方案。当上述消息中携带本发明实施例提供的码本方案的指示时，说明基站指示终端设备使用本发明实施例提供的码本方案。
综上所述，本发明实施例提供了如下一种码本结构：
W＝W1W2
其中W为所述基础码本，W1为波束码本，其行数等于基站的天线数量，W2为加权合并码本；
Figure PCTCN2017079346-appb-000055
G与天线阵列之中的第一组天线相对应，G′与天线阵列之中的第二组天线相对应；
Figure PCTCN2017079346-appb-000056
矩阵A和B均为列向量，且列向量A和B包含的非零元素的数量均大于1；列向量A的阶数等于矩阵G中列向量的数量，列向量B的阶数等于矩阵G′中列向量的数量。
可选的，G和G′中的列向量可以选自同一个列向量集合(列向量集合也可以称为波束集合)，也可以选自不同的列向量集合。来自同一列向量集合的列向量的阶数相同，来自不同列向量集合的列向量的阶数可以相同也可以不同。同一列向量集合内的列向量彼此可以正交也可以非正交。
可选的，G可以对应天线阵列之中的第一组天线，G′可以对应天线阵列之中的第二组天线。进一步的，每组天线内各天线的极化方向相同，第一组天线的极化方向与第二组天线的极化方向可以相同也可以不同。
本发明实施例提供的技术方案为每一组天线选择多个波束进行加权合并，以此来构造一个新的波束，并使用这个新的波束对这组天线进行加权。所构造的新的波束可以更加精准的模拟信道真实环境，提升预编码的精确度。
图6是依照本发明一实施例的CSI反馈方法600的示范性流程图。在具体实现过程中，方法600可由例如但不限于终端设备来执行。
步骤602，接收来自基站的下行符号，其中，该下行符号中包含导频。
步骤604，根据上述下行符号中包含的导频获得信道矩阵。
步骤606，根据上述信道矩阵和基础码本计算预编码矩阵。
步骤608，根据该预编码矩阵生成CSI。
步骤610，向基站发送上行符号，其中携带所述CSI。
上述步骤的具体执行细节以及涉及的具体特征，已经在上文结合图4～图5C进行了详细的描述，因此此处不再赘述。
图7是依照本发明一实施例的预编码方法700的示范性流程图。在具体实现过程中，方法700可由例如但不限于基站来执行。
步骤702，向终端设备发送下行符号，该下行符号406中携带导频。
步骤704，接收来自终端设备的上行符号，提取其中携带的CSI，其中，所述CSI由所述终端设备根据预编码矩阵生成，该预编码矩阵由所述终端设备根据信道矩阵和基础码本生成，该信道矩阵由所述终端设备根据所述导频生成。
步骤706，根据所述CSI生成预编码矩阵。
步骤708，根据所述预编码矩阵对需要发送给终端设备的调制符号进行预编码。如上文所述，在不同的场景(例如SU-MIMO和MU-MIMO)下，预编码过程中使用的预编码矩阵是不同的。
上述步骤的具体执行细节以及涉及的具体特征，已经在上文结合图4～图5C进行了详细的描述，因此此处不再赘述。
有关CSI的生成过程以及基础码本的内容，可参考上文结合图4和图5A～图5C的描述。
图8是依照本发明一实施例的终端设备800的硬件结构示意图。如图8所示，终端设备800包括处理器802、收发器804、多根天线806，存储器808、I/O(输入/输出，Input/Output)接口810和总线812。收发器804进一步包括发射器8042和接收器8044，存储器808进一步用于存储指令8082和数据8084。此外，处理器802、收发器804、存储器808和I/O接口810通过总线812彼此通信连接，多根天线806与收发器804相连。
处理器802可以是通用处理器，例如但不限于，中央处理器(Central Processing Unit，CPU)，也可以是专用处理器，例如但不限于，数字信号处理器(Digital Signal Processor，DSP)、应用专用集成电路(Application-Specific  Integrated Circuit，ASIC)和现场可编程门阵列(Field Programmable Gate Array，FPGA)等。此外，处理器802还可以是多个处理器的组合。处理器802用于执行，例如，图4所示终端设备404的CSI生成模块4044所执行的操作，以及图6所示方法600中的步骤604～608。处理器802可以是专门设计用于执行上述操作和/或步骤的处理器，也可以通过读取并执行存储器808中存储的指令8082，来执行上述操作和/或步骤，处理器802在执行上述操作和/或步骤的过程中可能需要用到数据8084。
收发器804包括发射器8042和接收器8044，其中，发射器8042用于通过多根天线806之中的至少一根天线向基站发送上行信号。接收器8044用于通过多根天线806之中的至少一根天线接收来自基站的下行信号。发射器8042具体用于通过多根天线806之中的至少一根天线执行，例如，图4所示终端设备404的发射模块4046所执行的操作，以及图6所示方法600中的步骤610。接收器8044具体用于通过多根天线806之中的至少一根天线执行，例如，图4所示终端设备404的接收模块4042所执行的操作，以及图6所示方法600中的步骤602。
存储器808可以是各种类型的存储介质，例如随机访问存储器(Random Access Memory，RAM)、只读存储器(Read-Only Memory，ROM)、非易失性随机访问存储器(Non-Volatile Random Access Memory，NVRAM)、可编程只读存储器(Programmable Read-Only Memory，PROM)、可擦除可编程只读存储器(Erasable Programmable Read-Only Memory，EPROM)、电可擦除PROM(Electrically Erasable PROM，EEPROM)、闪存、光存储器、寄存器等。存储器808具体用于存储指令8082和数据8084，处理器802可以通过读取并执行存储器808中存储的指令8082，来执行上文所述的操作和/或步骤，在执行上述操作和/或步骤的过程中可能需要用到数据8084。
I/O接口810用于接收来自外围设备的指令和/或数据，以及向外围设备输出指令和/或数据。
应注意，在具体实现过程中，终端设备800还可以包括其他硬件器件，本文不再一一列举。
图9是依照本发明一实施例的基站900的硬件结构示意图。如图9所示，基站900包括处理器902、收发器904、多根天线906，存储器908、I/O接口910和总线912。收发器904进一步包括发射器9042和接收器9044，存储器908进一步用于存储指令9082和数据9084。此外，处理器902、收发器904、存储器908和I/O接口910通过总线912彼此通信连接，多根天线906与收发器904相连。
处理器902可以是通用处理器，例如但不限于，CPU，也可以是专用处理器，例如但不限于，DSP、ASIC和FPGA等。此外，处理器902还可以是多个处理器的组合。处理器902用于执行，例如，图4所示基站402的预编码模块4026所执行的操作，以及图7所示方法700中的步骤706～708。处理器902可以是专门设计用于执行上述操作和/或步骤的处理器，也可以通过读 取并执行存储器908中存储的指令9082，来执行上述操作和/或步骤，处理器902在执行上述操作和/或步骤的过程中可能需要用到数据9084。
收发器904包括发射器9042和接收器9044，其中，发射器9042用于通过多根天线906之中的至少一根天线向终端设备发送下行信号。接收器9044用于通过多根天线906之中的至少一根天线接收来自终端设备的上行信号。发射器9042具体用于通过多根天线906之中的至少一根天线执行，例如，图4所示基站402的发射模块4022所执行的操作，以及图7所示方法700中的步骤702。接收器9044具体用于通过多根天线906之中的至少一根天线执行，例如，图4所示基站402的接收模块4024所执行的操作，以及图7所示方法700中的步骤704。
存储器908可以是各种类型的存储介质，例如RAM、ROM、NVRAM、PROM、EPROM、EEPROM、闪存、光存储器和寄存器等。存储器908具体用于存储指令9082和数据9084，处理器902可以通过读取并执行存储器908中存储的指令9082，来执行上文所述的操作和/或步骤，在执行上述操作和/或步骤的过程中可能需要用到数据9084。
I/O接口910用于接收来自外围设备的指令和/或数据，以及向外围设备输出指令和/或数据。
应注意，在具体实现过程中，基站900还可以包括其他硬件器件，本文不再一一列举。
本领域普通技术人员可知，上述方法中的全部或部分步骤可以通过程序指令相关的硬件完成，该程序可以存储于一计算机可读存储介质中，该计算机可读存储介质如ROM、RAM和光盘等。
综上所述，以上仅为本发明的较佳实施例而已，并非用于限定本发明的保护范围。凡在本发明的精神和原则之内，所作的任何修改、等同替换、改进等，均应包含在本发明的保护范围之内。

Claims (10)

  1. 一种信道状态信息CSI反馈方法，其特征在于，包括：
    接收来自基站的下行符号，其中，该下行符号中包含导频；
    根据该下行符号中包含的导频获得信道矩阵；
    根据该信道矩阵和基础码本计算预编码矩阵；
    根据该预编码矩阵生成CSI；
    向基站发送上行符号，其中，所述上行符号中携带所述CSI；
    其中，所述基站配置有天线阵列，所述基础码本为：
    W＝W1W2
    其中W为所述基础码本，W1为波束码本，其行数等于基站的天线数量，W2为加权合并码本；
    Figure PCTCN2017079346-appb-100001
    G与天线阵列之中的第一组天线相对应，G′与天线阵列之中的第二组天线相对应；
    Figure PCTCN2017079346-appb-100002
    矩阵A和B均为列向量，且列向量A和B中包含的非零元素数量均大于1；列向量A所包含的元素的数量等于矩阵G中列向量的数量，列向量B所包含的元素的数量等于矩阵G′中列向量的数量。
  2. 如权利要求1所述的方法，其特征在于，所述天线阵列中包含2N1N2根天线，第一组天线和第二组天线均包含N1N2根天线，且
    Figure PCTCN2017079346-appb-100003
    Figure PCTCN2017079346-appb-100004
    Ω为预设的一组N1N2×1阶向量，这些向量彼此正交或者非正交，L是向量的数量并且L≥2N1N2；G中的列向量彼此正交或者非正交；G′中的列向量彼此正交或者非正交；
    Figure PCTCN2017079346-appb-100005
    其中τ为第二组天线的极化方向与第一组天线的极化方向之间的交叉极化泄漏的值；
    Figure PCTCN2017079346-appb-100006
    Figure PCTCN2017079346-appb-100007
    其中，λi和φi为预设值，
    Figure PCTCN2017079346-appb-100008
    Figure PCTCN2017079346-appb-100009
    Figure PCTCN2017079346-appb-100010
    其中θ为第二组天线相对于第一组天线的相位旋转角度，γi和
    Figure PCTCN2017079346-appb-100011
    为预设值，
    Figure PCTCN2017079346-appb-100012
  3. 如权利要求1或2所述的方法，其特征在于，G与G′相同或者不同；A与B相同或者不同。
  4. 一种预编码方法，其特征在于，包括：
    接收来自终端设备的上行符号，提取其中携带的信道状态信息CSI，其中，所述CSI由所述终端设备根据预编码矩阵生成，该预编码矩阵由所述终端设备根据信道矩阵和基础码本生成，该信道矩阵由所述终端设备根据所述导频生成；
    根据所述CSI生成预编码矩阵；
    根据所述预编码矩阵对需要发送给终端设备的调制符号进行预编码；
    其中，所述基站配置有天线阵列，所述基础码本为：
    W＝W1W2
    其中W为所述基础码本，W1为波束码本，其行数等于基站的天线数量，W2为加权合并码本；
    Figure PCTCN2017079346-appb-100013
    G与天线阵列之中的第一组天线相对应，G′与天线阵列之中的第二组天线相对应；
    Figure PCTCN2017079346-appb-100014
    矩阵A和B均为列向量，且列向量A和B中包含的非零元素数量均大于1；列向量A所包含的元素的数量等于矩阵G中列向量的数量，列向量B所包含的元素的数量等于矩阵G′中列向量的数量。
  5. 如权利要求4所述的方法，其特征在于，所述天线阵列中包含2N1N2根 天线，第一组天线和第二组天线均包含N1N2根天线，且
    Figure PCTCN2017079346-appb-100015
    Figure PCTCN2017079346-appb-100016
    Ω为预设的一组N1N2×1阶向量，这些向量彼此正交或者非正交，L是向量的数量并且L≥2N1N2；G中的列向量彼此正交或者非正交；G′中的列向量彼此正交或者非正交；
    Figure PCTCN2017079346-appb-100017
    其中τ为第二组天线的极化方向与第一组天线的极化方向之间的交叉极化泄漏的值；
    Figure PCTCN2017079346-appb-100018
    Figure PCTCN2017079346-appb-100019
    其中，λi和φi为预设值，
    Figure PCTCN2017079346-appb-100020
    Figure PCTCN2017079346-appb-100021
    Figure PCTCN2017079346-appb-100022
    其中θ为第二组天线相对于第一组天线的相位旋转角度，γi和
    Figure PCTCN2017079346-appb-100023
    为预设值，
    Figure PCTCN2017079346-appb-100024
  6. 如权利要求4或5所述的方法，其特征在于，G与G′相同或者不同；A与B相同或者不同。
  7. 一种终端设备，其特征在于，包括：
    接收模块，用于接收来自基站的下行符号；
    信道状态信息CSI生成模块，用于根据该下行符号中包含的导频获得信道矩阵，根据该信道矩阵和基础码本计算预编码矩阵，根据该预编码矩阵生成CSI；
    发射模块，用于向基站发送上行符号，其中，所述上行符号中携带所述CSI；
    其中，所述基站配置有天线阵列，所述基础码本为：
    W＝W1W2
    其中W为所述基础码本，W1为波束码本，其行数等于基站的天线数量，W2为加权合并码本；
    Figure PCTCN2017079346-appb-100025
    G与天线阵列之中的第一组天线相对应，G′与天线阵列之中的第二组天线相对应；
    Figure PCTCN2017079346-appb-100026
    矩阵A和B均为列向量，且列向量A和B中包含的非零元素数量均大于1；列向量A所包含的元素的数量等于矩阵G中列向量的数量，列向量B所包含的元素的数量等于矩阵G′中列向量的数量。
  8. 如权利要求7所述的终端设备，其特征在于，所述天线阵列中包含2N1N2根天线，第一组天线和第二组天线均包含N1N2根天线，且
    Figure PCTCN2017079346-appb-100027
    Figure PCTCN2017079346-appb-100028
    Ω为预设的一组N1N2×1阶向量，这些向量彼此正交或者非正交，L是向量的数量并且L≥2N1N2；G中的列向量彼此正交或者非正交；G′中的列向量彼此正交或者非正交；
    Figure PCTCN2017079346-appb-100029
    其中τ为第二组天线的极化方向与第一组天线的极化方向之间的交叉极化泄漏的值；
    Figure PCTCN2017079346-appb-100030
    Figure PCTCN2017079346-appb-100031
    其中，λi和φi为预设值，
    Figure PCTCN2017079346-appb-100032
    Figure PCTCN2017079346-appb-100033
    Figure PCTCN2017079346-appb-100034
    其中θ为第二组天线相对于第一组天线的相位旋转角度，γi和
    Figure PCTCN2017079346-appb-100035
    为预设值，
    Figure PCTCN2017079346-appb-100036
  9. 一种基站，其特征在于，包括：
    发射模块，用于向终端设备发送下行符号，该下行符号中携带导频；
    接收模块，用于接收来自终端设备的信道状态信息CSI，其中，所述CSI由所述终端设备根据预编码矩阵生成，该预编码矩阵由所述终端设备根据信道矩阵和基础码本生成，该信道矩阵由所述终端设备根据所述导频生成；
    预编码模块，用于根据所述CSI生成预编码矩阵，以及根据所述预编码矩阵对需要发送给终端设备的调制符号进行预编码；
    其中，所述基站配置有天线阵列，所述基础码本为：
    W＝W1W2
    其中W为所述基础码本，W1为波束码本，其行数等于基站的天线数量，W2为加权合并码本；
    Figure PCTCN2017079346-appb-100037
    G与天线阵列之中的第一组天线相对应，G′与天线阵列之中的第二组天线相对应；
    Figure PCTCN2017079346-appb-100038
    矩阵A和B均为列向量，且列向量A和B中包含的非零元素数量均大于1；列向量A所包含的元素的数量等于矩阵G中列向量的数量，列向量B所包含的元素的数量等于矩阵G′中列向量的数量。
  10. 如权利要求9所述的基站，其特征在于，所述天线阵列中包含2N1N2根天线，第一组天线和第二组天线均包含N1N2根天线，且
    Figure PCTCN2017079346-appb-100039
    Figure PCTCN2017079346-appb-100040
    Ω为预设的一组N1N2×1阶向量，这些向量彼此正交或者非正交，L是向量的数量并且L≥2N1N2；G中的列向量彼此正交或者非正交；G′中的列向量彼此正交或者非正交；
    Figure PCTCN2017079346-appb-100041
    其中τ为第二组天线的极化方向与第一组天线的极化方向之间的交叉极 化泄漏的值；
    Figure PCTCN2017079346-appb-100042
    Figure PCTCN2017079346-appb-100043
    其中，λi和φi为预设值，
    Figure PCTCN2017079346-appb-100044
    Figure PCTCN2017079346-appb-100045
    Figure PCTCN2017079346-appb-100046
    其中θ为第二组天线相对于第一组天线的相位旋转角度，γi和
    Figure PCTCN2017079346-appb-100047
    为预设值，
    Figure PCTCN2017079346-appb-100048
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