CN107076824A - Apparatus and method for determining strut angle to carry out multiple-input and multiple-output downlink transfer - Google Patents
Apparatus and method for determining strut angle to carry out multiple-input and multiple-output downlink transfer Download PDFInfo
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- CN107076824A CN107076824A CN201480083290.9A CN201480083290A CN107076824A CN 107076824 A CN107076824 A CN 107076824A CN 201480083290 A CN201480083290 A CN 201480083290A CN 107076824 A CN107076824 A CN 107076824A
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- G—PHYSICS
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- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S3/00—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received
- G01S3/02—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received using radio waves
- G01S3/74—Multi-channel systems specially adapted for direction-finding, i.e. having a single antenna system capable of giving simultaneous indications of the directions of different signals
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- 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
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- 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
- H04B7/0686—Hybrid systems, i.e. switching and simultaneous transmission
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- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2626—Arrangements specific to the transmitter only
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Abstract
A kind of descending (DL) data flow control device of multiple-input and multiple-output (MIMO), the subset of the first strut angle and the second strut angle or the first strut angle pair and the second strut angle pair is configured to determine that, for carrying out downlink transfer from the antenna element of mimo antenna array.The subset of strut angle is determined according to one or more up (UL) signals received at the antenna element of the mimo antenna array.The element of the MIMO array is aligned to row and column at an angle to each other.The signal that the control device respectively receives units and row element is from the first support signal in the angled domain of space field transformation and the second support signal.Each support signal is the function of corresponding strut angle, and the support signal amplitude be the UL signals angle of arrival function.Based on the amplitude of the support signal, the control device determine strut angle to subset.
Description
Technical Field
The present invention relates to wireless communications, and more particularly, to a method and apparatus for transmitting and receiving data using a transmission angle selection technique, and mapping the data to be transmitted to the angles, and then transforming the data into a signal to be transmitted on a transmission antenna in a multiple-input multiple-output (MIMO) system having multiple antennas.
Background
Massive MIMO or very massive MIMO antenna systems are a technology that can provide large network capacity in a multi-user scenario, where a base station is equipped with a large number of antenna elements that serve multiple single-antenna users simultaneously. Additional antenna elements are generally less expensive and additional digital signal processing becomes less expensive. However, when there are many antennas, the link between the baseband unit and the remote antenna unit becomes a bottleneck to the rate when I-O (or in-phase and quadrature) antenna data (one stream per transmit antenna element) needs to be sent over this link to a large number of antennas. A low cost, low complexity solution to this problem is to select a subset of antenna elements out of the total number of antenna elements. With a certain number of RF chains and more antenna elements than this, antenna element selection can exploit spatial selectivity to boost system performance, and a subset of antenna elements can be selected and switched to RF chains. However, selecting a subset of antennas does not allow the system to benefit from the well-known benefits of using an excessively large number of antenna elements simultaneously for transmission (or reception) in a massive MIMO system. When transmitting and receiving at a base station, for example, over a large number of antenna elements in a massive MIMO antenna system, the propagation channel may provide more spatial selectivity and reduce interference to unintended users since the transmitted energy is more concentrated at the intended recipient, whereby system performance may be improved due to increased energy efficiency. Since higher data rates can be supported by massive MIMO, the spectral efficiency is also improved because as the number of antennas becomes large, the intra-cell interference and thermal noise are negligible.
Accordingly, there is a need to provide an apparatus and method for reducing backhaul requirements for the link between a remote antenna unit and a baseband unit in a MIMO or massive MIMO antenna system to be used for downlink transmission. Furthermore, there is a need to reduce the computational complexity when the number of antenna elements far exceeds the number of user data streams to be sent to the intended user.
Disclosure of Invention
It is an object of the present invention to provide an apparatus or system, and a method for reducing the computational complexity and backhaul requirements of a massive MIMO system when the number of user data streams is much smaller than the number of antennas. The method in the present invention determines a subset of support angles based on uplink signals received at antenna elements of one or more MIMO antenna arrays. The determined support angles may be used to map the downlink data streams onto a subset of the antenna elements of the MIMO antenna array.
The above object and other objects are achieved by the features of the independent claims. Other implementations are evident from the dependent claims, the description and the drawings.
According to a first aspect, there is provided a multiple-input multiple-output (MIMO) Downlink (DL) data flow control apparatus comprising at least one processor configured to: acquiring uplink signals (UL) received at antenna elements of one or more MIMO antenna arrays, the elements of the MIMO arrays being arranged in one or more rows or columns; for each of a selected number of rows, transforming the number of row signals from a spatial domain into a plurality of first support signals in an angular domain, wherein each first support signal of a given row is a function of a respective first support angle; for each of a selected number of columns, transforming the number of column signals from the spatial domain into a plurality of second support signals in the angular domain, wherein each second support signal of a given column is a function of a respective second support angle; determining a first set and a second set of support signal amplitudes by determining an amplitude of each or at least part of the first support signal and the second support signal; calculating a first average amplitude for each or at least part of the first support angles based on the amplitudes of the first support signals determined as a function of the same first support angles, and calculating a second average amplitude for each or at least part of the second support angles based on the amplitudes of the second support signals determined as a function of the same second support angles; comparing the first average amplitude value with a predetermined first threshold amplitude value and comparing the second average amplitude value with a predetermined second threshold amplitude limit value; and determining a subset of first support angles and a subset of second support angles, each angle of the subset of first angles having a respective first average magnitude exceeding the first threshold magnitude, each angle of the subset of second angles having a respective second average magnitude exceeding the second threshold magnitude.
In a first possible implementation form of the control device according to the first aspect, the at least one processor is configured to transform the number of row signals from a spatial domain to the plurality of first support signals in the angular domain using a Discrete Fourier Transform (DFT) or a Discrete Spatial Fourier Transform (DSFT), and to transform the number of column signals from the spatial domain to the plurality of second support signals in the angular domain.
In a second possible implementation form of the control apparatus according to the first aspect as such or according to the first implementation form of the first aspect, the at least one processor is further configured to determine the first subset of pairs of support angles or pairs of support angular coordinates by combining each angle of the subset of first support angles with each angle of the subset of second support angles.
In a third possible implementation form of the control apparatus according to the second implementation form of the first aspect, the at least one processor is further configured to: performing a two-dimensional transformation from a spatial domain to an angular domain on the signals of the selected row and the selected column by using the first support angle and the second support angle represented by the first subset of support angle pairs as discrete variables; determining, for each or at least part of the angles of the first subset of pairs of support angles, a magnitude of the respective two-dimensional transformation; comparing the determined two-dimensional transform amplitude to a third predetermined threshold amplitude; and determining pairs of support angles or a second subset of pairs of support angle coordinates, each angle of the second subset of pairs of support angles having a respective two-dimensional transformation amplitude exceeding the third threshold amplitude.
In a fourth possible implementation form of the control apparatus according to the second or third implementation form of the first aspect, the at least one processor is further configured to assign a plurality of Downlink (DL) data streams to a corresponding number of pairs of support angles for downlink transmission, wherein each pair of support angles is selected from the first subset or the second subset of pairs of support angles.
In a fifth possible implementation form of the control device according to the fourth implementation form of the first aspect, the at least one processor is further configured to transform the downstream data stream assigned to the support angle from the angle domain to the spatial domain using an Inverse Discrete Fourier Transform (IDFT).
In a sixth possible implementation form of the control apparatus according to the first aspect as such or according to any of the preceding implementation forms of the first aspect, the at least one processor is further configured to: estimating a new set of first support signal amplitudes based on the plurality of determined sets of first support signal amplitudes corresponding to the plurality of subsequently received uplink signals, the new set of first support signal amplitudes corresponding to a future point in time for receiving the uplink signal; estimating a new set of second support signal amplitudes based on the plurality of determined sets of second support signal amplitudes corresponding to the plurality of subsequently received uplink signals, the new set of second support signal amplitudes corresponding to the future point in time for receiving uplink signals; and calculating a first average amplitude and a second average amplitude based on the estimated new first support signal amplitude and second support signal amplitude.
In a seventh possible implementation form of the control device according to the fifth implementation form of the first aspect, the at least one processor is configured to estimate a new set of support signal amplitudes by using a time-linear estimation based on the determined amplitudes of the plurality of determined sets of support signal amplitudes.
In an eighth possible implementation form of the control device according to the sixth or seventh implementation form of the first aspect, the at least one processor is configured to estimate the new set of support signal amplitudes by using a moving time average or a weighted moving time average based on the determined amplitudes of the plurality of determined sets of support signal amplitudes.
In a ninth possible implementation form of the control apparatus according to the first aspect as such or according to any of the preceding implementation forms of the first aspect, the at least one processor is configured to, for a transformation of the row signals from the spatial domain to the angular domain and a transformation of the column signals from the spatial domain to the angular domain: forming a time signal matrix representing signal values received by the antenna elements in the selected row and the selected column, the rows and columns of the signal matrix corresponding to the selected row and the selected column of receiving elements; forming a frequency signal matrix by transforming the time signal matrix from a spatial time domain to a spatial frequency domain; transforming the signals of each row of the frequency signal matrix from the spatial frequency domain to an angular frequency domain, each row of the frequency signal matrix corresponding to a selected row of receiving elements; and transforming the signals of each column of the frequency signal matrix from the spatial frequency domain to an angular frequency domain, each column of the frequency signal matrix corresponding to a selected column of receiving elements. The transformation of the time signal matrix from the spatial time domain to the spatial frequency domain may be performed by Fourier Transform (FT) or Fast Fourier Transform (FFT) or any other fast implementation form of fourier transform, and its transformation from the spatial frequency domain to the angular frequency domain may be performed by Discrete Fourier Transform (DFT) or Discrete Spatial Fourier Transform (DSFT).
According to a second aspect, there is provided a method of determining a subset of supporting signals for transmitting a Downlink (DL) data stream from a plurality of antenna elements of one or more multiple-input multiple-output (MIMO) antenna arrays, the method comprising: receiving one or more uplink signals (UL) at antenna elements of one or more MIMO antenna arrays, the elements of the MIMO arrays being arranged in one or more rows and columns; for each of a selected number of rows, transforming the number of row signals from a spatial domain into a plurality of first support signals in an angular domain, wherein each first support signal of a given row is a function of a respective first support angle; for each of a selected number of columns, transforming the number of column signals from the spatial domain into a plurality of second support signals in the angular domain, wherein each second support signal of a given column is a function of a respective second support angle; determining a first set and a second set of support signal amplitudes by determining an amplitude of each or at least part of the first support signal and the second support signal; calculating a first average amplitude for each or at least part of the first support angles based on the amplitudes of the first support signals determined as a function of the same first support angle; calculating a second average amplitude for each or at least part of the second support angles based on the amplitude of the second support signal determined as a function of the same second support angle; comparing the first average amplitude value with a predetermined first threshold amplitude value and comparing the second average amplitude value with a predetermined second threshold amplitude limit value; and determining a subset of first support angles and a subset of second support angles, each angle of the subset of first angles having a respective first average magnitude exceeding the first threshold magnitude, each angle of the subset of second angles having a respective second average magnitude exceeding the second threshold magnitude.
In a first possible implementation form of the method according to the second aspect, the transformation of the number of row signals from the spatial transform domain to the plurality of first support signals in the angular domain and the transformation of the number of column signals from the spatial domain to the plurality of second support signals in the angular domain is performed using a Discrete Fourier Transform (DFT) or a Discrete Spatial Fourier Transform (DSFT).
In a second possible implementation form of the method according to the second aspect as such or according to the first implementation form of the second aspect, the method further comprises determining a first subset of pairs of support angles or pairs of support angular coordinates by combining each angle of the subset of first support angles with each angle of the subset of second support angles.
In a third possible implementation form of the method according to the second implementation form of the second aspect, the method further comprises: performing a two-dimensional transformation from a spatial domain to an angular domain on the signals of the selected row and the selected column by using the first support angle and the second support angle represented by the first subset of support angle pairs as discrete variables; determining, for each or at least part of the angles of the first subset of pairs of support angles, a magnitude of the respective two-dimensional transformation; comparing the determined two-dimensional transform amplitude to a third predetermined threshold amplitude; and determining pairs of support angles or a second subset of pairs of support angle coordinates, each angle of the second subset of pairs of support angles having a respective two-dimensional transformation amplitude exceeding the third threshold amplitude.
In a fourth possible implementation form of the method according to the second or third implementation form of the second aspect, the method further comprises assigning a plurality of Downlink (DL) data streams to a corresponding number of pairs of support angles for downlink transmission, wherein each pair of support angles is selected from the first subset or the second subset of pairs of support angles.
In a fifth possible implementation form of the method according to the fourth implementation form of the second aspect, the method further comprises transforming the downstream data stream mapped to the support angle from the angle domain to the spatial domain using an Inverse Discrete Fourier Transform (IDFT).
In a sixth possible implementation form of the method according to the second aspect as such or according to any of the preceding implementation forms of the second aspect, the step of determining the first and second sets of support signal amplitudes further comprises: estimating a new set of first support signal amplitudes based on the plurality of determined sets of first support signal amplitudes corresponding to the plurality of subsequently received uplink signals, the new set of first support signal amplitudes corresponding to a future point in time for receiving the uplink signal; and estimating a new set of second support signal amplitudes based on the plurality of determined sets of second support signal amplitudes corresponding to the plurality of subsequently received uplink signals, the new set of second support signal amplitudes corresponding to the future point in time for receiving uplink signals; the step of calculating the first and second average amplitudes is performed based on the estimated new first and second support signal amplitudes.
In a seventh possible implementation form of the method according to the sixth implementation form of the second aspect, the estimating of the new set of support signal amplitudes is performed by using a time-linear estimation based on the determined amplitudes of the plurality of determined sets of support signal amplitudes.
In an eighth possible implementation form of the method according to the sixth or seventh implementation form of the second aspect, the estimating of the new set of support signal amplitudes is performed by using a moving time average or a weighted moving time average based on the determined amplitudes of the plurality of determined sets of support signal amplitudes.
Drawings
FIG. 1 illustrates the delay in arrival time of a single plane wave projected onto a one-dimensional uniform linear array antenna or a uniform linear array of antenna elements;
FIG. 2 illustrates the delay in arrival time of a single plane wave projected onto a two-dimensional uniform rectangular array antenna or a uniform linear array of antenna elements;
fig. 3 is a block diagram illustrating transmission of an uplink signal from a user equipment, reception of the uplink signal at a base station, determination of a supporting angle at the base station, and transmission of a downlink signal using the supporting angle according to an embodiment of the present invention;
FIG. 4 is a block diagram illustrating processor configuration blocks of a control device according to an embodiment of the invention;
FIG. 5 is a block diagram of a processor configuration of a control device according to an embodiment of the invention, showing a different processing configuration corresponding to a portion of the configuration blocks of FIG. 4;
FIG. 6 is a block diagram of a processor configuration of a control device according to an embodiment of the invention, showing a different processing configuration corresponding to the last block of FIG. 3;
fig. 7 is a system diagram illustrating a data flow using a control device according to an embodiment of the present invention.
Detailed Description
It is an object of the present invention to reduce delay and improve accuracy when selecting spectral angles for Downlink (DL) data stream transmission using a large number of antenna elements of one or more (two-dimensional or multi-dimensional) massive MIMO antenna arrays. The DL data stream to be transmitted may be mapped to the selected supporting spectral angles and then an inverse fourier transform from the spectral angle domain to the spatial domain may be performed on the mapped DL signal. The resulting output of the inverse fourier transform may be mapped directly to antenna ports of the multi-dimensional antenna array. The following are within the scope of the objectives of the present application: (1) a subset of the supported spectral angles can be obtained on the uplink by using a single transmission of an Uplink (UL) Sounding Reference Signal (SRS) by a given User Equipment (UE) on a spatial average and used for downlink signal transmission. (2) In the angular domain of subsequent SRS transmissions, the obtained time average or weighted time average of the spectral magnitudes is used to determine subsequent updates that support the selected subset of spectral angles. The principles of the present invention may make the design and implementation of the precoder simpler by reducing delay and improving accuracy when selecting spectral angles based on the UL signal, where the selected spectral angles may have the largest spectral magnitudes and may be used as the spectral angles for transmitting data streams on the downlink.
The following is within the scope of embodiments of the invention: for a massive MIMO antenna array, when attempting to determine a subset of support spectral angles with the largest spectral magnitudes in another orthogonal spatial dimension (e.g., horizontal), an averaging operation may be performed in the spatial dimension (e.g., vertical) instead of performing a time averaging operation on magnitudes of time-varying angular domain signal strengths over multiple SRSs. When the spectral magnitude averaging operation in the angular domain for the spatial dimension (vertical) is completed, then a subset of support spectral angles may be selected for a given spatial dimension (horizontal) having the largest spatial (vertical) averaged spectral magnitude.
To determine the subset of support spectral angles with the largest spectral magnitudes in the other (vertical) spatial dimension, a similar procedure as just described may be applied, wherein the spectral magnitudes in the angular domain (vertical spatial dimension) are averaged in the other (horizontal) spatial dimension.
Note that time averaging or weighted time averaging may be performed on the two-dimensional array of spectral magnitudes in the angular domain to better select the subset of support angles corresponding to the largest spectral magnitudes.
Fig. 1 shows the delay in arrival time of a single plane wave impinging on a one-dimensional uniform linear array antenna, ULA and antenna 100. The antenna 100 has 5 antenna elements 1-5 arranged in a line, and a signal wave transmitted from a signal source is projected onto the antenna 100 at an arrival angle β from a direction perpendicular to the antenna 100. The distance between the two antenna elements 1 and 2 is d. Due to the moving distance dsin (β), the signal wave has a delay in arrival time from the element 1 to the element 2.
Fig. 2 shows the delay in arrival time of a single plane wave projected onto a two-dimensional uniform rectangular array antenna 200. The antenna 200 has 5 rows of equally spaced antenna elements 201 and 5 columns of equally spaced antenna elements 202, where the spacing between elements of the rows 201 is given by dH and the spacing between elements of the columns 202 is given by dV. A signal wave is emitted from the signal source 203, which is incident on the antenna 200 at an arrival angle θ H from a direction perpendicular to the line 201, and the delay in the arrival time of the signal wave from one element in a line to another is caused by the moving distance dHsin (θ H). The signal wave is incident on the antenna 200 at an arrival angle thetav from a direction perpendicular to the column 202, and the delay in the arrival time of the signal wave from one element to another element in a column is caused by the moving distance dVsin (thetav).
The principles of embodiments of the present invention are specifically analyzed below based on a single planar beam projected onto an antenna array as shown in fig. 2. However, the principle of the present invention is a general principle and is applicable to a case where there are a plurality of incident waves from different directions on an antenna array.
The invention covers embodiments in which the rows and columns of antenna elements may be arranged at an angle to each other, or may be arranged perpendicular to each other, but the angle need not be a right angle, other angles may be used, for example 60 degrees, 45 degrees or 30 degrees. In addition, for arranging elements in different rows, elements of a given row may be staggered left or right relative to elements of one or more adjacent rows. Elements in different columns may also be staggered with respect to elements of one or more adjacent columns. When receiving signals from several MIMO antenna arrays, the arrays may preferably be arranged in the same plane, i.e. coplanar.
The invention therefore also covers embodiments in which the rows and columns of antenna elements are not perpendicular. If they are not perpendicular, a first angle of arrival (azimuth) may be predicted and determined from signals received at row elements, and a second angle of arrival may be predicted and determined from signals received at column elements, where the columns may be at an angle other than 90 degrees (oblique columns) from the rows. At this time, the elevation angle may be determined based on the second angle of arrival obtained from the column elements and based on the first angle of arrival (azimuth angle) obtained from the row elements. If there are only rows of elements, the angle of arrival may be determined from only row elements.
For massive MIMO antenna arrays, one aspect of the present invention is described below with respect to determining a subset of supporting "spectral anglesFrom which a smaller subset of spectral angles is determinedWherein,and the collectionThe spectral angle in (b) will be used for downstream transmission. Can be mapped to these supporting spectral angles by inverse discrete fourier transformFrom the angular domain to the spatial domain. The inverse discrete fourier transformed stream outputs may then be mapped to antenna ports for transmission on the downlink. To simplify the symbols, assume the size of the rectangular antenna array has (M +1) rows and (M)2+1) column. To illustrate this concept, the following describes the process resulting from the projection of a single plane wave on an antenna array as shown in fig. 1 and/or fig. 2 above. Note that this method is a general method and is applicable to a case where there are a plurality of projections of waves from different directions on the antenna array. The following process assumes channel reciprocity and uses the signals received on the uplink to determine the subset of supporting signals to be used on the downlink.
In fig. 2, the incident signal wave has an arrival angle (AoA) θ with respect to a direction perpendicular to the line 201HAnd due to the movement distance tauHThe difference of (a), the signal wave has an arrival time delay dHsin (theta) from one element to another element in a rowH). The incident signal has an angle of arrival theta with the direction perpendicular to the columns 202VAnd the signal wave moves a distance dVsin (θ) from one element to another element in a columnV) Given time delay of arrival τV。
By using the line delay time tauHAnd column delay time τVFrom (M +1) × (M)2+1) the signals received upstream for each antenna element of the antenna array are given by the terms in the matrix r (t), r (t) being given by
The fourier transform may be performed by using a fourier transform, e.g., a Fourier Transform (FT) or a Fast Fourier Transform (FFT),the spatial signal represented by equation (1) is transformed into the frequency domain, where the signal is a function of space and time. In the frequency domain, the signal is a function of space and frequency, anIs given by
Step 1 of the process: for each row r of antenna elements, the received and detected signals srn(t),n＝1,…,M2+1 from the spatial time domain to the angular frequency domain or spectral angular domain, where n is the column index in equation (1), the signal is a function of frequency and angle. This can be done in two steps, first transforming the signal from the space-time domain (equation (1)) to the frequency domain or the space-frequency domain (equation (2)). The next step is then to transform the signal from the spatial frequency domain (equation (2)) to the angular frequency domain or spectral angular domain.
For a given angle of arrival (AoA), and having a value set to ωcGiven frequency ω, given delay τHAnd τHCan use Discrete Fourier Transform (DFT) or Discrete Spatial Fourier Transform (DSFT), and a certain number of discrete variables or discrete angles thetakTransform equation (2) to the angular frequency domain. The discrete variable θ of the number when transforming the row signal of equation (2)kCan be set equal to the number of elements in a row, which is equal to column M2+1 is equal in number, where θkIs set to k2 pi/M2K is 0 to M2。
Hereinafter, r is the row index of the two-dimensional antenna array, k is the discrete variable or θkAnd furthermore, for each row r, a number of first support signals in the angle domain are obtained by using DFT or DSFFT in equation (2), wherein each first support signal is a discrete first support angle θkFunction of (c):
r＝1,…,(M+1),k＝0,…,M2
equation (3) gives M2+1 value to yield Xr(θk) Each value corresponding to each antenna element in a row. When comparing equation (3) with FIG. 2, it should be noted that the discrete variable or discrete angle θkIs not the actual angle of arrival (AoA) but can be considered as an effective angle related to the angle of arrival. Each value Xr(θk) Is the delay time tauHIs also a function of the angle of arrival of the incident signal. Thus, according to θkDifferent value of (a) and different angle of arrival (AoA), Xr(θk) May also vary in size.
In equation (3), the selected row after the row signal is transformed has the same number of equally spaced elements, and the number of row signals is transformed from the spatial domain to the angular domain by the same number of θkA first support signal, wherein each first support signal of a given row may be a function of a respective first support angle, and the number of first support angles is equal to the number of elements in the row. However, since the granularity of the DSFT can be adjusted, the rows need not have the same number of elements and the row elements need not be equally spaced when using the DSTF for the transform. The resulting number of transformed first support signals and corresponding first support angles may then be determined by the selected granularity of the DSFT. The same applies to the selected columns.
Step 2: for each row index of antenna elements, by applying a first angle θ for each discretek，(k＝0,…,M2) Calculates the amplitude of the transformed first support signal to form a discrete first support spectral angle θkA vector of magnitudes of the indices. Obtaining the vector of each obtained line and forming a momentArraying:
and step 3: each element in the matrix of equation (4) represents the amplitude of the first support signal with a given first spectral angle. Performing column averaging on the elements of the matrix of equation (4):
selecting a first support spectral angle θjWherein the magnitude of the signal strength of equation (5) exceeds a threshold. This subset of first supported spectral angles may be used, for example, where each DL data stream is mapped to a unique spectral angle for DL transmission. This subset of first supported spectral angles is given by:
step 1-3, above, following the matrix X(r)Determines the support (support) or index of the first supported spectral angle. In the following step (4), a similar procedure is used, along the matrix X defined below(c)Determines the support or index of the second supported spectral angle.
Step 4, 5 and 6: using a similar procedure to steps 1, 2, 3, the signal is fourier transformed along one column of antenna elements, followed by an averaging calculation along the horizontal (row) dimension.
And 4, step 4: let c be the column index of the two-dimensional antenna array and k be θkThen for each column c of antenna elements, a certain number of second support signals in the angular domain are obtained, wherein each second support signal is a discrete second supportAngle thetakWherein θ iskIs set to k2 pi/M, k being 0 to M.
c＝1,…,(M2+1),k＝0,…,M
And 5: by indexing for each column of antenna elements, for each discrete second angle θk(k-0, …, M) calculating the magnitudes of the transformed second support signals to form a vector of magnitudes indexed by discrete second support spectral angles. Obtaining the vector of each obtained column and forming a matrix:
step 6: each element in the matrix of equation (8) represents the amplitude of the second support signal with a given second support angle. A line average is performed on the elements of the matrix of equation (8):
selecting a second support spectral angle θiWherein the magnitude of the signal strength exceeds a threshold:
step 7 (optional): for a certain number of uplink sounding reference signals received in the following time, steps 1-2 and 4-5 are performed for both rows and columns, so as to obtain a corresponding number of first support signal amplitudes (X of equation (4))(r)) And a second support signal amplitude (X of equation (8))(c)) And based on the determined number of first support signalsThe amplitude estimates a new set of first support signal amplitudes and estimates a new set of second support signal amplitudes based on the determined number of second support signal amplitudes. The estimation of the new set of first and second support signal amplitudes may be performed by using a time-linear estimation and/or using a moving time average or a weighted moving time average. Then, the first and second average amplitudes in steps 3 and 6 and equations (5) and (9) may be calculated based on the estimated new set of first and second support signal amplitudes, and the subsets may be selected in equations (6) and (10), respectivelyAnd subsets
And 8: once subset is completedAnd subsetsSelected, then the set of spectral angles to be used for DL transmission is aggregatedAnd (4) indexing.
The resulting collectionIs a first subset of pairs of support angles or pairs of support angle coordinates, wherein each pair comprises a subsetOf the first support angle and subsetOf the first support angle. SubsetsIs a subset of the first support angleEach corner of (a) and a subset of second support cornersIn combination with each corner of the panel.
First subset of support angle pairsMay be used for mapping to Downlink (DL) data streams, wherein each of a number of DL data streams is mapped to a data stream from the first subsetThe selected corresponding pair of support angles.
In order to obtain a more optimal set of support angle pairs, it is preferred to further reduce the obtained first subset of support angle pairsThe size of (2).
And step 9: from a first subset of pairs of support cornersSecond and final subsets of selected corner pairsFor DL data transmission on the basis of determining whether the magnitude of a given angular pair or the magnitude of a given angular coordinate pair in the angular domain exceeds a defined threshold, namely:
|X(θu,θv)|2>threshold_3 (11)
wherein, X (theta)u,θv) Is momentThe elements in the u row and v column of matrix X, the elements of matrix X being the two-dimensional transformation of matrix R (ω) from the spatial domain to the angular domain given by equation (2), where these elements are given by:
the expression R (omega) [ n, m ]]An element of the nth row and the mth column of the matrix R (ω) representing equation (2). Furthermore, a second subset of pairs of support angles or support coordinatesGiven by:
at this time, the second subset of the pair of support anglesMay be used for mapping to DL data streams, wherein each of a number of DL data streams is mapped from the second subsetThe selected corresponding pair of support angles.
Step 10: mapping Downlink (DL) data streams to a second subset of support angle pairsThe selected coordinate pair.
Support angle pairHas been determined in the angular frequency domain obtained using Discrete Fourier Transform (DFT) or Discrete Spatial Fourier Transform (DSFT). For transmitting the mapped DL data streamThe former return to the spatial frequency domain requires an inverse fourier transform (IDFT) or an inverse discrete fourier transform (IDSFT).
Step 11: an inverse fourier transform (IDFT) or an inverse discrete fourier transform (IDSFT) is performed on the mapped DL data stream.
The mapped DL data stream, which has now been transformed to the spatial frequency domain, needs to be transformed to the space-time domain, which can be done using an Inverse Fourier Transform (IFT).
Step 12: an Inverse Fourier Transform (IFT) from the frequency domain to the time domain is performed on the mapped DL data stream that has been transformed to the spatial frequency domain.
Thus, the transformed and angle-supported mapped DL data streams may be mapped to physical antenna ports of one or more MIMO antenna arrays for downlink transmission.
Step 13: and mapping the converted DL data streams subjected to supporting angle mapping to physical antenna ports of one or more MIMO antenna arrays for downlink transmission.
Fig. 3 is a block diagram illustrating transmission of an uplink signal from a user equipment 301, wherein the user equipment may be a mobile phone or a mobile device, and the uplink signal is a Sounding Reference Signal (SRS). The uplink signal SRS is received at the base station and the base station has control means according to an embodiment of the invention, and the base station is thus configured to determine the support angle to be mapped to the downlink signal 302. The control means of the base station is further configured to map the support angles to DL signals, transform the mapped DL signals, and forward the transformed DL signals to the antenna ports of the one or more MIMO antenna arrays 303.
Fig. 4 is a block diagram illustrating a processor configuration block of a control apparatus 400 according to an embodiment of the present invention. In block 401, a control apparatus 400 is configured to obtain one or more Uplink (UL) signals received at antenna elements of one or more MIMO antenna arrays. In block 402, the apparatus 400 is configured to perform processing to perform a transformation from a time domain to a frequency domain on the obtained UL signal, which may include the use of FT. In block 403, the apparatus is configured to perform spatial processing to perform a transform from a frequency domain to an angle domain on the frequency signal of block 402, which may include the use of a DFT. In block 404, the apparatus is configured to select pairs of subset support angles based on the transformed signal of block 403. In block 405, the apparatus is configured to map the pair of selected support angles to a Downlink (DL) signal or DL data stream. In block 406, the apparatus is configured to transform the mapped DL signal from the angular frequency domain to the spatial time domain, which may include the use of IDFT and IFT. In block 407, the apparatus is configured to map the converted DL signals from block 406 to physical antenna ports.
Fig. 5 is a block diagram of a processor configuration of a control device 500 according to an embodiment of the invention, showing different processing configurations corresponding to configuration blocks 401 and 404 of fig. 4.
In block 501, corresponding to 401 of fig. 4, a control apparatus 500 is configured to obtain one or more Uplink (UL) signals received at antenna elements of one or more MIMO antenna arrays. In block 502, the apparatus 500 is configured to perform a Fourier Transform (FT) on the obtained UL signal to obtain the result of equation (2), and thereby transform the received UL signal from a space-time domain to a space-frequency domain. In block 503, the apparatus 500 is configured to perform a Discrete Fourier Transform (DFT) or a Discrete Spatial Fourier Transform (DSFT) on the fourier transformed rows and columns of equation 2, thereby transforming the signal of equation (2) from the spatial frequency domain to the angular frequency domain. In block 504, the apparatus 500 is configured to select the rows of transformed signals of block 503 to obtain a number of first support signals, each being a function of a respective first support angle and corresponding to the result of equation (3) in step 1 above. In block 505, the apparatus 500 is configured to select the columns of transformed signals of block 503 to obtain a number of second support signals, each signal being a function of the corresponding second support angle and corresponding to the result of equation (7) in step 4 above. In block 506, the apparatus 500 is configured to determine or estimate the magnitudes of the first support signal and the second support signal corresponding to the results of equation (4) in step 2 and equation (8) in step 5.
In both block 507 and block 508 (both optional), apparatus 500 is configured to repeat steps 1-2 and 4-5 for a number of uplink Sounding Reference Signals (SRS) received in a subsequent time, thereby obtaining a corresponding number of first and second support signal amplitudes, which correspond to X of equation (4)(r)And X of equation (8)(c)(block 507) and estimating a new set of first and second support signal amplitudes based on the determined plurality of first and second support signal amplitudes (block 508). In block 509, the apparatus 500 is configured to calculate an average amplitude of the first support signal and the second support signal, which corresponds to equation (5) of step 3 and equation (9) of step 6, based on the amplitudes obtained from block 506 or block 508, and the apparatus 500 is further configured to compare the obtained average amplitude with a predetermined threshold amplitude, which corresponds to equation (6) of step 3 and part of equation (10) of step 6. In block 510, the apparatus 500 is configured to select a first subset of pairs of first and second support angles, determined by the first and second support angles, for which the average amplitude of the respective first and second support signals is greater than a predetermined threshold amplitude, corresponding to the selected first and second subsets of support angles of equation (6) of step 3 and equation (10) of step 6; and further configured to index the selected first and second support angles in the set of support angles, corresponding to step 8. In block 511, the apparatus 500 is configured to reduce the first subset of pairs of first and second support angles, thereby determining a reduced second subset of pairs of first and second support angles, which is described in step 9 and equation (11), equation (12), and equation (13).
Fig. 6 is a block diagram of a processor configuration of a control device 600 according to an embodiment of the invention, showing a different processing configuration corresponding to block 303 of fig. 3. A downlink signal or a downlink data stream to be transmitted is received at block 601. In block 602, the apparatus 600 is configured to map the pair of selected support angles to a Downlink (DL) signal or a Downlink (DL) data stream. In block 603, the apparatus 600 is configured to transform the mapped DL signal from the angular frequency domain back to the spatial frequency domain, which may include an IDFT. In block 604, the apparatus 600 is configured to forward and map the transformed DL signals mapped to the support signals to antenna ports of one or more MIMO antenna arrays for downlink transmission. In block 605, the apparatus is configured to transform the mapped DL signal from the spatial frequency domain back to the spatial time domain, which may include IFTs, before the mapped DL signal is finally transmitted. In block 606, the device is configured to map the converted DL signals from block 605 to physical antenna ports for downlink transmission, i.e., Transmission (TX) in DL.
Fig. 7 is a system diagram illustrating a data flow using a control device according to an embodiment of the present invention. In fig. 7, an uplink sounding reference signal (UL SRS)701 is received by one or more antenna elements of a MIMO antenna array and forwarded to a base station including a control apparatus according to an embodiment of the present invention. The control apparatus processes the received UL SRS signals at 702 in order to determine first and second support signals having respective first and second support angles. The control means further processes the obtained first and second support signals at 702 in order to determine or select a subset of pairs of first and second support angles, and the pairs of the selected subset of support angles 704, 705 are mapped to a Downlink (DL) data stream 706. The DL signals or DL data streams 706 mapped to the support angles 704, 705 in the angular domain are transformed from the angular frequency domain back to the spatial frequency domain using an Inverse Discrete Fourier Transform (IDFT) (707), then transformed from the spatial frequency domain to the spatial time domain using an Inverse Fourier Transform (IFT) (708), and further forwarded and mapped by the control means of the base station to antenna ports 709, 710 of one or more MIMO antenna arrays for downlink transmission.
The effect of the invention is to be able to reduce the delay in obtaining a subset of the supporting spectral angles for data transmission in a massive MIMO system. The delay is reduced from the duration of time that multiple sparse SRSs need to be received to the duration of time that a single SRS is received. An additional benefit is that large-scale MIMO antenna arrays of large size can be used to improve the accuracy of selecting the subset of support spectral angles with the largest spectral magnitudes. This approach facilitates data transmission in 3gpp lte advanced systems and other systems using massive MIMO.
The principles of the present invention can be applied to systems using massive MIMO antennas in wireless networks and have channel state information of an uplink channel when channel reciprocity is supported or channel state information of a downlink channel when channel reciprocity is not supported. The principles of the present invention may be applied to two or more antenna arrays, or to sub-arrays in an antenna array.
While the invention has been described in conjunction with specific features and embodiments, it is evident that various modifications and implementations can be made thereto without departing from the spirit and scope of the application. Accordingly, the specification and figures are to be regarded in an illustrative manner, and are intended to cover any modifications, variations, combinations, or equivalents, which may be included within the scope of the invention.
The word "comprising" as used in the appended claims does not exclude other elements or steps. The use of the word "a" or "an" in the appended claims does not exclude a plurality.
Claims (15)
1. A multiple-input multiple-output (MIMO) Downlink (DL) data flow control apparatus (400, 500, 600) comprising at least one processor configured to:
acquiring uplink signals (UL) (401, 501, 701) received at antenna elements of one or more MIMO antenna arrays (200), the elements of the MIMO arrays being arranged in one or more rows (201) or columns (202);
for each of a selected number of rows (201), transforming the number of row signals from a spatial domain into a plurality of first support signals (504) in an angular domain, wherein each first support signal of a given row is a function of a respective first support angle;
for each of a selected number of columns (202), transforming the number of column signals from a spatial domain into a plurality of second support signals (505) in an angular domain, wherein each second support signal of a given column is a function of a respective second support angle;
determining a first set and a second set of support signal amplitudes (506) by determining an amplitude (504, 505) of each of the first support signal and the second support signal or at least part of the signals;
calculating a first average amplitude (509) for each of the first support angles or at least part of the angles based on the amplitudes of the first support signals determined as a function of the same first support angle, and calculating a second average amplitude (509) for each of the second support angles or at least part of the angles based on the amplitudes of the second support signals determined as a function of the same second support angle;
comparing (509) the first average amplitude to a predetermined first threshold amplitude and the second average amplitude to a predetermined second threshold amplitude (509); and
a subset of first support angles and a subset of second support angles are determined (404, 510), each angle of the subset of first angles having a respective first average magnitude exceeding the first threshold magnitude, and each angle of the subset of second angles having a respective second average magnitude exceeding the second threshold magnitude.
2. The apparatus of claim 1, wherein the at least one processor is configured to determine a first subset of support angle pairs or support angle coordinate pairs by combining each angle of the subset of first support angles and each angle of the subset of second support angles (510).
3. The apparatus of claim 2, wherein the at least one processor is configured to:
performing a two-dimensional transformation from a spatial domain to an angular domain on the signals of the selected row and the selected column by using the first support angle and the second support angle represented by the first subset of support angle pairs as discrete variables;
determining, for each or at least part of the angles in the first subset of pairs of support angles, a magnitude of the respective two-dimensional transformation;
comparing the determined two-dimensional transform amplitude to a third predetermined threshold amplitude; and
determining (511) pairs of support angles or a second subset of pairs of support angle coordinates, each angle of the second subset of pairs of support angles having a respective two-dimensional transformation amplitude exceeding the third threshold amplitude.
4. The apparatus of claim 2 or 3, wherein the at least one processor is further configured to allocate a plurality of Downlink (DL) data streams (601, 706) to a corresponding number of support angle pairs (602, 704, 705) for downlink transmission, wherein each support angle pair is selected (703) from the first or second subset of support angle pairs.
5. The apparatus of any of claims 1-4, wherein the at least one processor is further configured to:
estimating a new set of first support signal amplitudes (507, 508) based on the plurality of determined sets of first support signal amplitudes corresponding to a plurality of subsequently received uplink signals, the new set of first support signal amplitudes corresponding to future points in time for receiving uplink signals;
estimating a new set of second support signal amplitudes (507, 508) based on the plurality of determined sets of second support signal amplitudes corresponding to the plurality of subsequently received uplink signals, the new set of second support signal amplitudes corresponding to the future point in time for receiving uplink signals; and
based on the estimated new first and second support signal amplitudes, first and second average amplitudes are calculated (509).
6. The apparatus of claim 5, wherein the at least one processor is configured to estimate a new set of support signal amplitudes using a time-linear estimation based on the determined amplitudes of the plurality of determined sets of support signal amplitudes.
7. The apparatus of claim 5 or 6, wherein the at least one processor is configured to estimate a new set of support signal amplitudes by using a moving time average or a weighted moving time average based on the determined amplitudes of the plurality of determined sets of support signal amplitudes.
8. The apparatus of any preceding claim, wherein for a transformation of a row signal from a spatial domain to an angular domain and a transformation of a column signal from a spatial domain to an angular domain, the at least one processor is configured to:
forming a time signal matrix representing signal values received by said antenna elements in said selected row and said selected column, the rows and columns of said signal matrix corresponding to said selected row and said selected column of receiving elements;
forming a frequency signal matrix (502) by transforming the time signal matrix from a spatial time domain to a spatial frequency domain;
transforming (503) signals of each row of the frequency signal matrix from the spatial frequency domain to an angular frequency domain, each row of the frequency signal matrix corresponding to a selected row of receiving elements; and
transforming signals of each column of the frequency signal matrix from the spatial frequency domain to an angular frequency domain (504), each column of the frequency signal matrix corresponding to a selected column of receiving elements.
9. A method of determining a subset of supporting signals for transmitting a Downlink (DL) data stream from a plurality of antenna elements (709, 710) of one or more multiple-input multiple-output (MIMO) antenna arrays, the method comprising:
receiving one or more uplink signals (UL) (401, 501, 701) at antenna elements of one or more MIMO antenna arrays (200), the elements of the MIMO array being arranged in one or more (201) and columns (202);
for each of a selected number of rows (201), transforming the number of row signals from a spatial domain into a plurality of first support signals (504) in an angular domain, wherein each first support signal of a given row is a function of a respective first support angle;
for each of a selected number of columns (202), transforming the number of column signals from a spatial domain into a plurality of second support signals (505) in an angular domain, wherein each second support signal of a given column is a function of a respective second support angle;
determining a first set and a second set of support signal amplitudes (506) by determining an amplitude (504, 505) of each or at least part of the first support signal and the second support signal;
calculating a first average amplitude (509) for each or at least part of the first support angles based on the amplitudes of the first support signals determined as a function of the same first support angle;
calculating a second average amplitude (509) for each or at least part of the second support angles based on the amplitudes of the second support signals determined as a function of the same second support angle;
comparing (509) the first average amplitude to a predetermined first threshold amplitude;
comparing (509) the second average magnitude to a predetermined second threshold; and
a subset of first support angles and a subset of second support angles are determined (404, 510), each angle of the subset of first angles having a respective first average magnitude exceeding the first threshold magnitude, and each angle of the subset of second angles having a respective second average magnitude exceeding the second threshold magnitude.
10. The method of claim 9, further comprising determining a first subset of support angle pairs or support angle coordinate pairs by combining each angle of the subset of first support angles and each angle of the subset of second support angles (510).
11. The method of claim 10, further comprising:
performing a two-dimensional transformation from a spatial domain to an angular domain on the signals of the selected row and the selected column by using the first support angle and the second support angle represented by the first subset of support angle pairs as discrete variables;
determining, for each or at least part of the angles of the first subset of pairs of support angles, a magnitude of the respective two-dimensional transformation;
comparing the determined two-dimensional transform amplitude to a third predetermined threshold amplitude; and
determining (511) pairs of support angles or a second subset of pairs of support angle coordinates, each angle of the second subset of pairs of support angles having a respective two-dimensional transformation amplitude exceeding the third threshold amplitude.
12. The method of claim 10 or 11, further comprising allocating a plurality of Downlink (DL) data streams (601, 706) to a corresponding number of support angle pairs (602, 704, 705) for downlink transmission, wherein each support angle pair is selected (703) from the first or second subset of support angle pairs.
13. The method of any of claims 9-12, wherein determining the first and second sets of support signal amplitudes further comprises:
estimating a new set of first support signal amplitudes (507, 508) based on the plurality of determined sets of first support signal amplitudes corresponding to a plurality of subsequently received uplink signals, the new set of first support signal amplitudes corresponding to future points in time for receiving uplink signals; and
estimating a new set of second support signal amplitudes (507, 508) based on the plurality of determined sets of second support signal amplitudes corresponding to the plurality of subsequently received uplink signals, the new set of second support signal amplitudes corresponding to the future point in time for receiving uplink signals; wherein,
the calculation of the first and second average amplitudes is based on the estimated new first and second support signal amplitudes (509).
14. The method of claim 13, wherein estimating a new set of support signal amplitudes is based on the determined amplitudes of the plurality of determined sets of support signal amplitudes using a time-linear estimation.
15. The method of claim 13 or 14, wherein the estimation of the new set of support signal amplitudes is based on the determined amplitudes of the plurality of determined sets of support signal amplitudes by using a moving time average or a weighted moving time average.
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| CN107076824B (en) | 2020-04-14 |
| WO2016074706A1 (en) | 2016-05-19 |
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