CN107181519B - Null steering expansion 3D-MIMO beam forming method based on moving target DOA - Google Patents

Null steering expansion 3D-MIMO beam forming method based on moving target DOA Download PDF

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CN107181519B
CN107181519B CN201710556742.6A CN201710556742A CN107181519B CN 107181519 B CN107181519 B CN 107181519B CN 201710556742 A CN201710556742 A CN 201710556742A CN 107181519 B CN107181519 B CN 107181519B
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theta
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doa
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CN107181519A (en
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胡欣
李博
王卫东
刘帅军
崔高峰
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Beijing University of Posts and Telecommunications
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    • 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
    • H04B7/0617—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 for beam forming
    • 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
    • H04B7/08—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station
    • H04B7/0837—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station using pre-detection combining
    • H04B7/0842—Weighted combining
    • H04B7/086—Weighted combining using weights depending on external parameters, e.g. direction of arrival [DOA], predetermined weights or beamforming

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Abstract

The invention discloses a null steering expansion 3D-MIMO beamforming method based on moving target DOA, belonging to the field of interference suppression. Firstly, on the basis of the existing 3D-MIMO beam forming, aiming at a communication base station and a certain mobile terminal, an antenna array with M multiplied by N array elements is constructed on an xy plane; respectively calculating the weight of each array factor; determining DOA information between a target mobile terminal and an interference mobile terminal and a base station; then, the weight of each array factor is readjusted according to the DOA information; finally, by applying constraints to the desired direction and the angular region around the undesired direction, null-steering expansion is performed in the undesired direction while leaving no distortion in the desired direction. The problem that the interference suppression capability is reduced when the null width is narrow in a user mobility scene is solved, and the robustness of the system is improved, so that the interference of position change is effectively suppressed, the expected signal is well approximate to a non-distortion correspondence, and the spectrum efficiency is effectively improved to meet the requirement of higher rate.

Description

Null steering expansion 3D-MIMO beam forming method based on moving target DOA
Technical Field
The invention belongs to the field of interference suppression, and particularly relates to a null steering expansion 3D-MIMO beamforming method based on moving target DOA.
Background
According to the description of '5G vision and demand white paper', a 5G supported wide area coverage scene provides a user with an experience density of up to 10Mbit/s, and a data traffic density of a hot spot region can reach 10Gbit/s experience rate and 10Tbit/km2 data density. However, the conventional MIMO antennas not only have a small number and poor controllability, but also have low performance and heavy application of spatial multiplexing, spatial diversity, and beamforming functions, which are not acceptable in 5G.
The 3D-MIMO technology is one of the 5G key technologies, the spatial degree of freedom in the vertical direction is increased on the basis of the 2D-MIMO technology, the system capacity can be improved, the spectrum efficiency can be increased, and the inter-cell interference can be effectively reduced. Companies started to push 3D-MIMO beamforming technology from the initial stage of LTE Rel-11 standardization, while more and more operators and equipment manufacturer enterprises have shown enthusiasm for 3D-MIMO beamforming technology in the preparation stage of Rel-12.
The working principle of the intelligent antenna mainly comprises two processes, firstly, an antenna system estimates the direction of arrival (DOA) of a multipath signal transmitted from a mobile terminal, and spatial filtering is carried out after the distance, the downward inclination angle and the azimuth angle between the mobile terminal and a base station are calculated, so that the interference of other terminals to the base station is inhibited; secondly, the base station adjusts the amplitude and the phase weight of signals on each oscillator of the antenna according to the DOA information, and carries out digital beam forming on the signals sent by the intelligent antenna, so that the main lobe of the signals sent by the base station can be sent back to the mobile terminal along the arrival direction of the electric wave signals of the mobile terminal with a smaller lobe angle and higher power density, thereby the main lobe direction of the electromagnetic waves sent by the intelligent antenna is aligned to the expected user, and the zero lobe direction is aligned to the interference source.
Obviously, the core of the smart antenna is the generation of beam forming and the positioning of the formed beam, and the formed beam can accurately position the user terminal even if the formed beam with extremely high power density and longer radiation distance is generated.
The beamforming of the MIMO antenna is a signal preprocessing technique based on an antenna array, which generates a beam with directivity by adjusting the weighting coefficient of each array element in the antenna array, thereby obtaining an obvious array gain. If the weighting coefficient of each array element can be properly controlled according to the channel condition, the interference to the undesired direction can be reduced as much as possible while the signal strength of the desired direction is enhanced. If the weighting coefficient is obtained by the DOA parameter preprocessing of the terminal, the beam forming can be directed to the terminal user. However, the existing beamforming technology is adjusted based on DOA information of signal estimation when the user is in a stationary state, and in a user mobility scenario, beamforming performance is seriously degraded.
A 3D-MIMO beamforming system needs a set of schemes to determine weights, so as to adjust beam pointing direction, so that a beam is pointed to an ideal user terminal, and nulls are formed in the direction of non-ideal users to mitigate interference. This increases the signal to interference and noise ratio and mitigates interference from other side lobes. Therefore, a set of weight determination methods is needed to construct the weights of the horizontal and vertical arrays respectively, and minimize the mean square error of the array pattern vector and the unit vector, where the unit vector represents the array pattern in the ideal direction and the zero vector represents the array pattern in the non-ideal direction. Since a rectangular planar array can be viewed as an array of M N-dimensional lines, the weights of the M-N dimensional array can be derived from the weights of the horizontal and vertical arrays, respectively.
The beam steering and null steering method mainly depends on angle domain information to generate a shaped weight, and when a user moves, the uncertainty of the position of a user terminal can influence the accuracy of DOA estimation in the direction of arrival, so that the interference suppression performance of the beam shaping technology is reduced. The null formed by the traditional beamforming method is narrow, and interference signals can be well inhibited when the direction of arrival of the signals is accurately estimated. In practice, however, due to the change of the DOA signal, interference may be caused to mismatch with the null position and the desired signal direction by a proper amount, so that the signal output by beamforming contains the interference signal that is not suppressed. Steering vector mismatch can lead to degraded beamforming performance.
Disclosure of Invention
On the basis of the existing 3D-MIMO beamforming, the invention provides a moving target DOA-based null-steering expansion 3D-MIMO beamforming method aiming at the problem that the interference suppression capability is reduced when the null steering width is narrow in a user mobility scene and in order to restrain the null steering width, obtain beamforming with more stable performance such as side lobe gain and weight vector module value.
The method comprises the following specific steps:
step one, aiming at a communication base station and a certain mobile terminal, constructing an antenna array with M multiplied by N array elements on an xy plane;
selecting a horizontal ground as an x-axis, wherein M array elements are arranged on the x-axis, a horizontal ground perpendicular to the x-axis is a y-axis, and N array elements are arranged on the y-axis;
step two, respectively calculating the weight of each array factor in the antenna array;
array factor weight w of m-nmnThe calculation is as follows:
wmn＝am·bn
amthe weight of the array factor of the m-n in the x-axis direction is referred to; bnThe weight of the m-n array factor in the y-axis direction is referred to.
Step three, according to the positions of the target mobile terminal and the interference mobile terminal, respectively determining DOA information between each terminal and the base station;
the target mobile terminal is a mobile terminal communicating with the base station;
DOA between the target mobile terminal and the base station is set to
Figure BDA0001345961460000021
DOA between an interfering mobile terminal and a base station is set to
Figure BDA0001345961460000022
1,2,3, … …; an angle estimation deviation due to mobility of the terminal is set as
Figure BDA0001345961460000023
All DOA angles take an x axis as an initial edge of the angle;
fourthly, readjusting the weight of each array factor according to the DOA information between each terminal and the base station;
the method comprises the following specific steps:
step 401, setting the horizontal value AF of each array factor in M × N array elementsxAnd the value AF of each array factor in the vertical directionyObtaining an expression of each array factor by using a directional diagram product principle;
Figure BDA0001345961460000031
dxas between two adjacent array factors on the x-axisDistance, dyIs the distance between two adjacent array factors on the y-axis.
k is an integer of adjustment coefficient βxIndicating the phase delay in the horizontal direction, βyIndicating the phase delay in the vertical direction, (theta, phi) is the value of the angle between each terminal and the base station;
step 402, bringing in DOA information between each terminal and the base station, setting the value of the array factor expression corresponding to the target mobile terminal to 1, and setting the value of the array factor expression corresponding to the interfering mobile terminal to 0;
the results are as follows:
Figure BDA0001345961460000032
step 403, according to the values of the array factor expressions, using the horizontal values AF of each array factorxCalculating the weight W in the horizontal directionx；
First, AF is calculated according to the value of each line factor in the horizontal directionxFormula, calculating the weight WxThe expression of (1);
Figure BDA0001345961460000033
wherein, Wx＝[a1a2…aM]T；
Then, in the expected direction, according to the value of the array factor expression corresponding to the target mobile terminal being 1, obtaining:
Figure BDA0001345961460000034
in an unexpected direction, according to the value of an array factor expression corresponding to the interfering mobile terminal being 0, obtaining:
Figure BDA0001345961460000035
finally, the weight W is matchedxSolving the expression;
Figure BDA0001345961460000036
is provided with
Figure BDA0001345961460000041
B＝[1 0…0]TThe above formula is simplified to AWx＝B；
Wx＝A-1B, A is a reversible matrix of M × M, WxPinv (a) B, pinv (a) is the Moore-Penrose generalized inverse.
Step 404, utilizing the vertical values AF of each array factor according to the values of each array factor expressionyCalculating the weight W of the vertical directiony；
First, AF is determined according to the value of each array factor in the vertical directionyFormula, calculating the weight WyThe expression of (1);
Figure BDA0001345961460000042
wherein, Wy＝[b1b2…bN]T；
Then, in the expected direction, according to the value of the array factor expression corresponding to the target mobile terminal being 1, obtaining:
Figure BDA0001345961460000043
in an unexpected direction, according to the value of an array factor expression corresponding to the interfering mobile terminal being 0, obtaining:
Figure BDA0001345961460000044
finally, the weight W is matchedySolving the expression;
Figure BDA0001345961460000045
is provided with
Figure BDA0001345961460000046
B'＝[1 0…0]TThe above formula is simplified to A' Wy＝B'；
Wy＝A'-1B ', A' is an invertible matrix of N × N, WyPinv (a '). times.b ', pinv (a ') is the Moore-Penrose generalized inverse.
Step 405, using the weight W in the horizontal directionxAnd weight W in the vertical directionyCalculating a weight matrix W of the array antenna, and further obtaining a weight value after each array factor is adjusted;
W＝Wx(Wy)T＝(wmn)M×N
fifthly, applying the weight of each adjusted array factor, and performing null-steering expansion in the undesired direction by applying constraint on angle areas around the desired direction and the undesired direction, and simultaneously having no distortion in the desired direction;
the null extension includes two parts: DOA signal θ in a desired direction0Expansion to [ theta ]0l,θ0h]And DOA signal theta in an undesired directioniExpansion to [ theta ]il,θih]。
The method specifically comprises the following steps: to extend the DOA signal theta in undesired directionsiWhen theta isi∈[θil,θih]The time array satisfies: | wHs(θi) If | is less than or equal to thetaiExpansion to [ theta ]il,θih](ii) a A null response constraint threshold;
to extend the DOA signal theta in a desired direction0When theta ∈ [ theta ]0l,θ0h]Time theta0Is nearly distortion-free and satisfies wHs (theta) -1 is less than or equal to mu, then theta0Expansion to [ theta ]0l,θ0h](ii) a Mu is a minimum value.
The invention has the advantages that:
1) compared with the traditional beamforming scheme, the null-steering expansion 3D-MIMO beamforming method based on the moving target DOA effectively improves the spectrum efficiency in the aspect of wireless technology to meet the requirement of higher speed.
2) In a moving target, when the signal estimation is not accurate, the effective receiving range of the signal is expanded by effectively widening the null, array response constraint to expected and interference directions, side lobe control constraint and other modes are applied, and the system robustness is improved when the moving target and the larger signal DOA are estimated to have deviation.
Drawings
FIG. 1 is a diagram of a terminal user mobility scenario in 3D-MIMO according to the present invention;
FIG. 2 is a flowchart of a null-steering expansion 3D-MIMO beamforming method based on moving object DOA according to the present invention;
FIG. 3 is a geometric distribution diagram of the active area array factor of the present invention;
fig. 4 is a smart antenna beam forming 3D antenna pattern of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples.
The invention relates to an end user mobility scenario in 3D-MIMO (3-Dimensional Multiple-Input Multiple-Output), as shown in FIG. 1, θ0Representing the initial horizontal angle, theta, from the mobile terminal to the BS1Indicating the horizontal direction angle after the movement; Δ θ represents an angle difference; d0Representing the initial distance between the base station and the mobile terminal; d1Indicating the distance of the mobile terminal from the base station after movement. t is t0Denotes the initial time, t1Indicates the time after the movement, and Δ t indicates the time difference.
Aiming at a base station BS and a mobile terminal MES in communication, when the target terminal enters an interference area, the change of an incident signal DOA or the existence of an estimation error causes the reduction of beam forming performance, and a wider null is formed at the interference position through null broadening, so that the interference of position change is effectively inhibited, and a desired signal is better approximate to a non-distortion correspondence.
As shown in fig. 2, the specific steps are as follows:
step one, aiming at a communication base station and a certain mobile terminal, constructing an antenna array with M multiplied by N array elements on an xy plane;
for a rectangular planar array on an x-y plane, as shown in fig. 3, M array elements are arranged on an x axis, and N array elements are arranged on a y axis, so as to form an antenna array with M × N array elements, wherein the rectangular planar array can be regarded as M linear arrays of N array elements or N linear arrays of M array elements.
Figure BDA0001345961460000061
Denotes a horizontal azimuth angle of the array antenna, theta denotes a vertical elevation angle, dxAnd dyRespectively representing the horizontal and vertical direction spacing of the antenna array; u denotes a received signal.
Step two, respectively calculating the weight of each array factor in the antenna array;
the weight value of the m-n array element is wmnThe calculation is as follows:
wmn＝am·bn
amthe weight of the array factor of the m-n in the x-axis direction is referred to; bnThe weight of the m-n array factor in the y-axis direction is referred to.
Step three, according to the positions of the target mobile terminal and the interference mobile terminal, DOA information between each terminal and the base station is respectively calculated;
the target mobile terminal is a mobile terminal communicating with the base station;
in this embodiment, the DOA between the target mobile terminal and the base station is set as
Figure BDA0001345961460000062
DOA between an interfering mobile terminal and a base station is set to
Figure BDA0001345961460000063
And
Figure BDA0001345961460000064
an angle estimation deviation due to mobility of the terminal is set as
Figure BDA0001345961460000065
All DOA angles take an x axis as an initial edge of the angle;
fourthly, readjusting the weight of each array factor according to the DOA information between each terminal and the base station;
the method comprises the following specific steps:
step 401, setting the horizontal value AF of each array factor in M × N array elementsxAnd the value AF of each array factor in the vertical directionyObtaining an expression of each array factor by using a directional diagram product principle;
knowing the array factors of the independent action of the antenna arrays of M array elements or N array elements, the antenna array directional diagram of the whole array elements of M multiplied by N is obtained by the directional diagram multiplication principle, and the antenna array directional diagram is obtained by the directional diagram multiplication principle:
Figure BDA0001345961460000066
dxis the distance between two adjacent array factors on the x-axis, dyIs the distance between two adjacent array factors on the y-axis.
k is an integer of adjustment coefficient βxIndicating the phase delay in the horizontal direction, βyIndicating the phase delay in the vertical direction, and when beam phasing is required,
Figure BDA0001345961460000067
wherein theta is0And
Figure BDA0001345961460000068
representing phase modulation to theta0And
Figure BDA0001345961460000069
and (4) an angle. (theta, phi) is the angle value between each terminal and the base station;
step 402, bringing in DOA information between each terminal and the base station, setting the value of the array factor expression corresponding to the target mobile terminal to 1, and setting the value of the array factor expression corresponding to the interfering mobile terminal to 0;
in order to be able to receive a signal in a desired direction,and minimizes the effect of undesired directions. It is necessary to make the desired direction produce unity gain so that AF is 1; and a zero point is formed in an undesired direction so that AF becomes 0. I.e. in the desired direction: AFx＝1and AFy1 is ═ 1; with AF in an undesired directionx＝0and AFy＝0。
In order to be able to receive signals in a desired direction and to minimize the influence of undesired directions; it is necessary to produce unity gain in the desired direction, i.e.
Figure BDA0001345961460000071
While forming a zero point in an undesired direction, i.e.
Figure BDA0001345961460000072
Step 403, according to the values of the array factor expressions, using the horizontal values AF of each array factorxCalculating the weight W in the horizontal directionx；
First, AF is calculated according to the value of each line factor in the horizontal directionxFormula, calculating the weight WxThe expression of (1);
Figure BDA0001345961460000073
wherein, Wx＝[a1a2…aM]T；
Then, in the expected direction, according to the value of the array factor expression corresponding to the target mobile terminal being 1, obtaining:
Figure BDA0001345961460000074
in an unexpected direction, according to the value of an array factor expression corresponding to the interfering mobile terminal being 0, obtaining:
Figure BDA0001345961460000075
in the inventionIn which there are four beams with theta in the desired direction0，
Figure BDA0001345961460000076
The other three undesired directions respectively have
Figure BDA0001345961460000077
Figure BDA0001345961460000078
Figure BDA0001345961460000079
In the undesired direction, it is possible to obtain:
Figure BDA00013459614600000710
Figure BDA00013459614600000711
Figure BDA00013459614600000712
finally, the weight W is matchedxSolving the expression;
Figure BDA0001345961460000081
is provided with
Figure BDA0001345961460000082
B＝[1 0…0]TThe above formula is simplified to AWx＝B；
Wx＝A-1B, A is a reversible matrix of 4 × M, and the weight W in the horizontal dimensionxPinv (a) B, pinv (a) is the Moore-Penrose generalized inverse.
Step 404, according to eachValues of the array factor expression, using the values AF of the factors per array in the vertical directionyCalculating the weight W of the vertical directiony；
First, AF is determined according to the value of each array factor in the vertical directionyFormula, calculating the weight WyThe expression of (1);
Figure BDA0001345961460000083
wherein, Wy＝[b1b2…bN]T；
Then, in the expected direction, according to the value of the array factor expression corresponding to the target mobile terminal being 1, obtaining:
Figure BDA0001345961460000086
in an unexpected direction, according to the value of an array factor expression corresponding to the interfering mobile terminal being 0, obtaining:
Figure BDA0001345961460000084
finally, the weight W is matchedySolving the expression;
Figure BDA0001345961460000085
is provided with
Figure BDA0001345961460000091
B'＝[1 0…0]TThe above formula is simplified to A' Wy＝B'；
Wy＝A'-1B ', A' is an invertible matrix of N × N, WyPinv (a '). times.b ', pinv (a ') is the Moore-Penrose generalized inverse.
Step 405, using the weight W in the horizontal directionxAnd weight W in the vertical directionyCalculating a weight matrix W of the array antenna, and further obtaining a weight value after each array factor is adjusted;
W＝Wx(Wy)T＝(wmn)M×N
since the mobility of the user may affect the estimation on the angle of arrival:
Figure BDA0001345961460000092
θ1＝θ0+Δθ
Figure BDA0001345961460000093
wherein, thetatmp＝θ0+(π-θv)，Δd＝v×Δt，0≤Δt＜Tud。
Fifthly, applying the weight of each adjusted array factor, and performing null-steering expansion in the undesired direction by applying constraint on angle areas around the desired direction and the undesired direction, and simultaneously having no distortion in the desired direction;
the null formed by the traditional beam forming method is narrow, and interference signals can be well inhibited when the arrival direction of the signals is accurately estimated. In practice, however, due to the change of the motion signal DOA of the user, interference may be caused to be misaligned with the null position and misdirected to the desired signal; the null steering expansion technology can effectively solve the problem that the beamforming performance is reduced when the interference signal moves;
the null extension includes two parts: DOA signal θ in a desired direction0Expansion to [ theta ]0l,θ0h]And DOA signal theta in an undesired directioniExpansion to [ theta ]il,θih]。
The method specifically comprises the following steps: interfering signal movement
Suppose desired signal DOA is θ0With interference signal DOA at [ theta ]il,θih]Internal variations, in order to better receive the desired signal and suppress the interfering signal, the array accordingly needs to satisfy:
H(θ0)＝wHs(θ0)＝1
H(θi)＝|wHs(θi)|≤
θi∈[θil,θih]a null response constraint threshold;
controlling the beam pattern sidelobe gain to be less than a certain threshold eta, and then the array response of the sidelobe area needs to meet the requirement
|wHs(θΘ)|≤η
Where Θ represents the angular range covered by the sidelobe region.
Desired signal motion
When the desired signal is within a certain range [ theta ]0l,θ0h]For internal changes, to obtain a better expected response, the requirement of [ theta ] is satisfied0l,θ0h]In range near without distortion, i.e.
wHs(θ)-1≤μ
Wherein, theta ∈ [ theta ]0l,θ0h]Mu is a minimum value.
Selecting discrete angle information at equal intervals within the DOA angle range of the expected signal
wHs(θ0t)-1≤μ,t＝1,2,…,T
Wherein T is the number of the selected discrete angles; suppose that K fixed interference signals are respectively from thetaikK is 1,2, …, incident in the K direction, the constraint in the interference direction is
H(θik)≤，k＝1,2,…,K
The method mainly comprises two steps:
and selecting a proper precoding matrix according to the DOE information, and forming the null in the direction.
The received signal can be written as
y＝HPx
Where H is the channel vector and P is the precoding matrix
DFT codebook is selected as candidate beam forming matrix, precoding based on DFT codebook has better beam directivity in linear array, design process can be simplified, and precoding matrix can be written into
Figure BDA0001345961460000101
G denotes the codebook size, P(g)(m, n) denotes an m-th row n-th column of the precoding matrix.
Figure BDA0001345961460000102
Representing the g-th precoding matrix.
Suppose a line array has NtAn antenna array spaced by a half-wavelength
Figure BDA0001345961460000103
Array corresponding factors can be written as
Figure BDA0001345961460000104
Order to
Figure BDA0001345961460000111
Figure BDA0001345961460000112
Suppose that
Figure BDA0001345961460000113
Is composed of
Figure BDA0001345961460000114
Line m, such that the zero point can be obtained by
Figure BDA0001345961460000115
Figure BDA0001345961460000116
Obtained from the precoding matrix.
The finally formed null-steering expansion intelligent antenna beam forming 3D antenna directional diagram based on the moving target DOA is shown in figure 4.

Claims (4)

1. A null steering expansion 3D-MIMO beamforming method based on moving object DOA is characterized by comprising the following specific steps:
step one, aiming at a communication base station and a certain mobile terminal, constructing an antenna array with M multiplied by N array elements on an xy plane;
selecting a horizontal ground as an x-axis, wherein M array elements are arranged on the x-axis, a horizontal ground perpendicular to the x-axis is a y-axis, and N array elements are arranged on the y-axis;
step two, respectively calculating the weight of each array factor in the antenna array;
array factor weight w of m-nmnThe calculation is as follows:
wmn＝am·bn
amthe weight of the array factor of the m-n in the x-axis direction is referred to; bnThe weight of the m-n array factor in the y-axis direction is referred to;
step three, according to the positions of the target mobile terminal and the interference mobile terminal, respectively determining DOA information between each terminal and the base station;
DOA between the target mobile terminal and the base station is set to
Figure FDA0002474003060000011
DOA between an interfering mobile terminal and a base station is set to
Figure FDA0002474003060000012
An angle estimation deviation due to mobility of the terminal is set as
Figure FDA0002474003060000013
All DOA angles take an x axis as an initial edge of the angle;
Figure FDA0002474003060000014
representing the horizontal azimuth angle of the array antenna, and theta represents the vertical direction elevation angle;
fourthly, readjusting the weight of each array factor according to the DOA information between each terminal and the base station;
the method comprises the following concrete steps:
step 401, setting the horizontal value AF of each array factor in M × N array elementsxAnd the value AF of each array factor in the vertical directionyObtaining an expression of each array factor AF by using a directional diagram product principle;
Figure FDA0002474003060000015
wherein d isxIs the distance between two adjacent array factors on the x-axis, dyIs the distance between two adjacent array factors on the y axis, k is an adjustment coefficient and is a positive integer βxIndicating the phase delay in the horizontal direction, βyIndicating the phase delay in the vertical direction, (theta, phi) is the value of the angle between each terminal and the base station;
step 402, bringing in DOA information between each terminal and the base station, setting the value of the array factor expression corresponding to the target mobile terminal to 1, and setting the value of the array factor expression corresponding to the interfering mobile terminal to 0;
the results are as follows:
Figure FDA0002474003060000016
step 403, according to the values of the array factor expressions, using the horizontal values AF of each array factorxCalculating the weight W in the horizontal directionx；
Step 404, utilizing the vertical values AF of each array factor according to the values of each array factor expressionyCalculating the weight W of the vertical directiony；
Step 405, using the weight W in the horizontal directionxAnd weight W in the vertical directionyCalculating a weight matrix W of the array antenna, and further obtaining a weight value after each array factor is adjusted;
W＝Wx(Wy)Τ＝(wmn)M×N
and step five, applying the weight of each adjusted array factor, and applying constraint to angle areas around the expected direction and the unexpected direction to perform null-steering expansion in the unexpected direction without distortion in the expected direction.
2. The method as claimed in claim 1, wherein the step 403 specifically includes the following steps:
first, AF is calculated according to the value of each line factor in the horizontal directionxFormula, calculating the weight WxThe expression of (1);
Figure FDA0002474003060000021
wherein, Wx＝[a1a2…aM]T；
Then, in the expected direction, according to the value of the array factor expression corresponding to the target mobile terminal being 1, obtaining:
Figure FDA0002474003060000022
in an unexpected direction, according to the value of an array factor expression corresponding to the interfering mobile terminal being 0, obtaining:
Figure FDA0002474003060000023
finally, the weight W is matchedxSolving the expression;
Figure FDA0002474003060000024
is provided with
Figure FDA0002474003060000025
B＝[1 0…0]ΤThe above formula is simplified to AWx＝B；
Wx＝A-1B, A is M × MAn inverse matrix; wxPinv (a) B, pinv (a) is the Moore-Penrose generalized inverse.
3. The method as claimed in claim 1, wherein the step 404 is as follows specifically:
first, AF is determined according to the value of each array factor in the vertical directionyFormula, calculating the weight WyThe expression of (1);
Figure FDA0002474003060000026
wherein, Wy＝[b1b2…bN]T；
Then, in the expected direction, according to the value of the array factor expression corresponding to the target mobile terminal being 1, obtaining:
Figure FDA0002474003060000031
in an unexpected direction, according to the value of an array factor expression corresponding to the interfering mobile terminal being 0, obtaining:
Figure FDA0002474003060000032
finally, the weight W is matchedySolving the expression;
Figure FDA0002474003060000033
is provided with
Figure FDA0002474003060000034
B'＝[1 0…0]ΤThe above formula is simplified to A' Wy＝B'；
Wy＝A'-1B ', A' is an invertible matrix of N × N, WyPinv (a '). B ', pinv (A ') is Moore-Penrose generalized inverse.
4. The moving object DOA-based null-steering extension 3D-MIMO beamforming method of claim 1 wherein the null steering extension in the fifth step includes two parts: DOA signal θ in a desired direction0Expansion to [ theta ]0l,θ0h]And DOA signal theta in an undesired directioniExpansion to [ theta ]il,θih](ii) a The method specifically comprises the following steps:
to extend the DOA signal theta in undesired directionsiWhen theta isi∈[θil,θih]The time array satisfies: | wHs(θi) If | is less than or equal to thetaiExpansion to [ theta ]il,θih](ii) a A null response constraint threshold;
to extend the DOA signal theta in a desired direction0When theta ∈ [ theta ]0l,θ0h]Time theta0Is nearly distortion-free and satisfies wHs (theta) -1 is less than or equal to mu, then theta0Expansion to [ theta ]0l,θ0h](ii) a Mu is a minimum value.
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