CN116388814A - Large-scale MIMO (multiple input multiple output) multi-connection structure-based simulation and hybrid precoding method - Google Patents
Large-scale MIMO (multiple input multiple output) multi-connection structure-based simulation and hybrid precoding method Download PDFInfo
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Abstract
The large-scale MIMO analog precoding method based on the multi-connection structure comprises the following steps: step 1: solving an analog precoding matrix F RF The first Q-1 submatrices of (a); step 2: solving an analog precoding matrix F RF The Q sub-matrix of the step 1 and the step two are assembled to form an analog precoding matrix F RF . The invention also discloses a large-scale MIMO based on the multi-connection structure. According to the invention, based on the multi-connection structure, according to the difference of channel gains from the transmitting antenna to different receiving antennas, a higher analog precoding gain can be obtained through the multi-connection structure and the transmitting antenna successive maximization channel gain algorithm, and finally the overall mixed precoding gain and the spectrum efficiency of the system are obviously improved.
Description
Technical Field
The invention belongs to the technical field of wireless communication, and relates to a large-scale MIMO (multiple input multiple output) simulation and hybrid precoding method based on a multi-connection structure.
Background
Massive MIMO (massive multiple-input multiple-output) can greatly improve the spectral efficiency and power efficiency of a system by configuring tens to hundreds of antennas at a base station and combining simple transmit precoding and receive combining processing, and has become a key technology of wireless communication systems such as fifth-generation mobile communication (5G) and post-5G. Theoretically, massive MIMO in the downlink requires the use of all-digital precoding to obtain optimal system performance. However, the digital processing of the baseband requires that each array element of the antenna array has an independent radio frequency link, resulting in a drastic rise in complexity, cost and power consumption over conventional MIMO, which greatly limits the practical application of massive MIMO. Thus, researchers have proposed an analog-to-digital hybrid precoding scheme with fewer radio frequency links than base station antennas. The basic idea is as follows: the precoding is decomposed into two parts, baseband low-dimensional digital precoding and radio frequency high-dimensional analog precoding, and the latter is typically implemented using a simple phase shifter.
Fig. 1 shows a schematic diagram of a full connection structure and a partial connection structure of a general massive MIMO hybrid precoder. In the fully connected configuration shown in fig. 1a, each rf link is connected to all the transmitting antennas through phase shifters, so the number of phase shifters required is equal to the product of the number of rf links and the number of transmitting antennas; many antennas require hundreds or even thousands of phase shifters, resulting in extremely high hardware costs and power consumption. In the partial connection structure shown in fig. 1b, each radio frequency link is only connected with the transmitting antennas in a certain subarray, that is, each transmitting antenna can only be connected with one radio frequency link, so that the number of required phase shifters is equal to the number of antennas, and compared with the full connection structure, the hardware cost and the power consumption are greatly reduced. The large-scale MIMO mixed precoding of the two connection structures can be applied to the two situations of a single user terminal and a multi-user terminal.
A full connection structure. For the case of multi-user terminals, literature [ Liang L, et al Low-complexity hybrid precoding in massive multiuser MIMO systems [ J ]. IEEE Wireless Communications Letters,2014,3 (6): 653-656 ] proposes a hybrid precoding method of "analog precoding based on air channel coefficient phase information+digital precoding based on equivalent channel matrix inversion". The method has the main advantages that the phase information of the air channel coefficient is directly extracted to generate the analog precoding matrix, and the simple closed solutions of the analog precoding matrix and the digital precoding matrix are respectively obtained with extremely low complexity. For the single user terminal situation, the digital precoding based on the inversion of the equivalent channel matrix is replaced by the digital precoding based on the singular value decomposition of the equivalent channel matrix.
And part of the connecting structure. For the single user terminal case, literature [ Ming Zhu, et al Low-complexity partially-connected hybrid precoding for massive MIMO systems [ C ]. Proceedings of IEEE Wireless Communications & Networking Conference (WCNC), 2020:1-6 ] proposes a hybrid precoding method of "fixed subarray and sequence+analog precoding based on air channel coefficient phase information+digital precoding based on singular value decomposition of equivalent channel matrix". For the situation of a multi-user terminal, literature [ Zhang Lei, etc. ] a large-scale MIMO hybrid precoder and matching relation [ P ]. ZL202010844421.8,2022-03-11 ] proposes a hybrid precoding method of 'fixed subarray and ordering + analog precoding based on air interface channel coefficient phase information + digital precoding based on inverse of an equivalent channel matrix'. The common characteristics of the two methods are: the antenna subarrays are of a fixed centralized design, and each radio frequency link is connected with the corresponding subarray in a sequential or sequencing mode; the phase information of the air channel coefficient is directly extracted to generate an analog precoding matrix, and the analog precoding gain of equal gain transmission is realized, so that the acceptable overall performance can be obtained with extremely low complexity.
The hybrid precoding technology based on the full connection structure has better performance, but the hardware cost and the power consumption are extremely high. Hybrid precoding techniques based on partial connection structure also suffer from the disadvantages: firstly, although the number of phase shifters can be greatly reduced, the inherent characteristics determine that the performance of the phase shifter is not less different than that of a full-connection structure; secondly, the antenna subarray is designed in a fixed and centralized manner, the space degree of freedom of the large-scale MIMO system is not fully utilized, and enough analog precoding gain cannot be obtained, so that the overall hybrid precoding performance is improved greatly.
The applicant builds the precoding method disclosed in the application number 2023101141665, namely the hybrid precoding method based on the dynamic subarray in the ultra-large-scale MIMO, on the basis that the channel matrix of the ultra-large-scale MIMO system has the block sparse characteristic, needs to consider and control the spectrum efficiency difference among users, and is suitable for the hybrid precoding of the ultra-large-scale MIMO system (the channel matrix has the block sparse characteristic), so that the universality is not enough.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention discloses a large-scale MIMO simulation and mixed precoding method based on a multi-connection structure.
The invention discloses a large-scale MIMO analog precoding method based on a multi-connection structure, which is characterized by comprising the following steps of: the method comprises the following steps:
step 1: solving an analog precoding matrix F RF The first Q-1 submatrices of (a);
initially setting q=1;
step 101. Traversing the transmitting antenna n TX Each antenna in= (q-1) km+1, (q-1) km+2, qKM, at the nth of the channel matrix H TX Column all K channel coefficients
J of which the amplitude is the largest is selected, and the corresponding receiving antenna number is marked as +.>
q=1, 2,; j is multiple connection factors of 1-N RF ；
Step 102, simulating a precoding matrix F RF Is the first of (2)
Individual elements
Wherein the method comprises the steps of
Representing the element +.>
Is a phase of (2);
step 103, if the channel coefficient corresponding to a certain receiving antenna is selected to JM times in the traversal process, deleting the channel coefficient from the candidate set in the subsequent selection process;
step 104, respectively making q=2, 3 and … Q-1; repeating steps 101-103;
step 2: solving an analog precoding matrix F RF Is the Q sub-matrix of (2);
Wherein the method comprises the steps of
Representing the element +.>
Is a phase of (2);
step 3, collecting all elements obtained in the step 1 and the step two, and combining to form an analog precoding matrix F RF ；
The channel matrix
k is the number of receiving antennas, N TX And N RF The number of transmitting antennas and the number of radio frequency links at the base station end are respectively, and M=N TX /N RF The method comprises the steps of carrying out a first treatment on the surface of the JM is the number of antennas that each radio frequency link can connect.
Preferably, the multiple connection factor j=1 or N RF 。
The large-scale MIMO multi-connection structure-based hybrid precoding method comprises the steps of calculating a digital precoding matrix, wherein the calculation method of the digital precoding matrix is any one of the following two methods:
method 1:
calculating an equivalent channel matrix g=hf RF ，
Performing singular value decomposition on G, i.e.
G＝UΣV H (2)
In the above description, U, Σ, and V represent a left singular matrix, a singular value matrix, and a right singular matrix of the equivalent channel matrix G, respectively, and the superscript H represents conjugate transpose of the matrices;
taking the front N of right singular matrix V S Columns, i.e. digital precoding matrix F BB ＝V(1:N S )，N S For independent data streams to be transmitted.
Method 2:
digital precoding matrix
Wherein the equivalent channel matrix g=h×f RF H is a channel matrix, and the superscript H of G represents Hermitian transpose operation of the matrix F A friendship Luo Beini us (Frobenius) norm representing a matrix, K being the total number of receiving antennas;
h and F RF Channel matrix and analog precoding matrix according to claim 1 or 2, respectively.
Large-scale MIMO based on multiple connection structure, each antenna can be connected with J radio frequency links, each radio frequency link can be connected with JM antennas, and the number of required phase shifters is J.times.N TX ；
Wherein m=n TX /N RF ；N TX And N RF The number of transmitting antennas and the number of radio frequency links at the base station end are respectively.
Compared with the prior art, the invention has the following beneficial effects:
firstly, according to the multi-connection structure provided by the invention, according to the difference of channel gains from a transmitting antenna to different receiving antennas, an analog precoding factor set corresponding to the transmitting antenna is generated by utilizing a transmitting antenna successive maximization channel gain algorithm, and dynamic subarrays corresponding to radio frequency links are combined and constructed. Through the multi-connection structure and the transmitting antenna successive maximization channel gain algorithm, higher analog precoding gain can be obtained, and finally the overall mixed precoding gain and the frequency spectrum efficiency of the system are obviously improved.
And based on a more general multi-connection structure, the number of radio frequency links to which each antenna can be connected depends on a multi-connection factor J, and the number of phase shifters required is the product of the multi-connection factor and the number of transmitting antennas, so that various choices are provided for the trade-off among performance, hardware cost and power consumption.
Secondly, the invention does not need to change the physical form and the array structure of the large-scale antenna of the base station, only carries out dynamic subarray division on the base station, and provides great flexibility for system design.
And the method is characterized in that the method comprises the step of searching a plurality of coefficients with the largest amplitude in a limited number of channel coefficients, wherein the method comprises the step of searching the coefficients with the largest amplitude in the limited number of channel coefficients, and the added calculation complexity is smaller than the calculation amount of the whole precoding flow, including matrix multiplication, matrix inversion or singular value decomposition, for solving the equivalent channel matrix and the digital precoding matrix.
Drawings
Fig. 1 is a schematic diagram of a conventional massive MIMO hybrid precoder, fig. 1a is a full connection structure, and fig. 1b is a partial connection structure.
Fig. 2 is a schematic diagram of a massive MIMO multi-connection-based architecture according to an embodiment of the present invention.
Fig. 3 is a schematic diagram of a simulation comparing the spectral efficiency of the system of the present invention and the prior art method in the case of a single user terminal in an independent Rayleigh fading channel.
Fig. 4 is a schematic diagram of a simulation comparing the spectral efficiency of the system of the present invention and the prior art method in the case of a multi-user terminal in an independent Rayleigh fading channel.
In the figure: 201 radio frequency links, 202 analog precoders, 203 dynamic sub-array generators, 204 phase shifters.
Detailed Description
The following detailed description of the invention is, therefore, not to be taken in a limiting sense, and is set forth in the appended drawings.
A schematic diagram of the structure of a multi-connection structure and dynamic subarray based analog precoder in massive MIMO hybrid precoding is given as shown in fig. 2.
The invention does not directly relate to receiving end processing, but for convenience of description, the number of receiving antennas is set as K: for the single user terminal case, it can be assumed that the terminal has K receiving antennas; for the case of multi-user terminals, it may be assumed that there are K single-antenna user terminals, totaling K receive antennas. Setting the number of transmitting antennas and the number of radio frequency links at the base station endAre respectively N TX And N RF The number of independent data streams to be transmitted is N S 。
The above parameters satisfy the constraint condition
N S ≤K≤N RF ≤N TX . Let m=n TX /N RF The multiple connection factor is J (J is more than or equal to 1 and N is more than or equal to N) RF )
In the multi-connection structure, each RF link may be connected to JM antennas, each antenna may be connected to J RF links, and the number of required phase shifters is J×N TX . Thus, the proposed multiple connection structure can be regarded as a generalization of the traditional full connection structure and the partial connection structure, namely: when j=1, the multiple connection structure is degraded to a partial connection structure; when j=n RF In this case, the multi-connection structure is evolved into a full-connection structure.
Assuming that the base station can obtain channel information from each transmitting antenna to all receiving antennas, the basic process flow is as follows.
The massive MIMO hybrid precoder for transmitting signals from a base station to a user terminal mainly comprises three modules, namely a radio frequency link 201, an analog precoder 202 and a digital precoder. The main sub-modules of the analog precoder 202 are a dynamic sub-array generator 203 and a phase shifter 204. Original data stream 1 to data stream N S Processing by a digital precoder to obtain N RF The baseband data streams; this N RF The baseband data streams are then input to the analog precoder 202 via the radio frequency link 201, and the analog precoder 202 generates an analog precoding matrix F RF And acts on K baseband data streams to output N TX The signals to be transmitted.
In the analog precoder 202, a sub-module dynamic sub-array generator 203 constructs dynamic sub-arrays corresponding to all radio frequency links according to the "transmitting antenna successive maximization channel gain algorithm", a sub-module phase shifter 204 generates phase shift values for corresponding transmitting antennas according to the "transmitting antenna successive maximization channel gain algorithm", and the dynamic sub-array generator 203 and the phase shifter 204 jointly determine an analog precoding matrix F RF Is calculated by the computer.
At the base station end, N is output by the digital precoder RF The dimension baseband data vector x is input to the analog precoder 202 for analog precoding to obtain an output signal N TX The dimension vector y, i.e., the analog precoder 202, builds the input data N RF Dimension vector x and output data N TX Mapping relation y=f between dimension vectors y RF x, N contained in output data y TX The path signal is finally formed by N TX The antennas transmit separately. At the user end, the user terminal receives the pre-coded signal sent by the base station, and the user terminal can recover the self-expected signal after simple receiving processing.
The system model and basic problems used in the present invention are described below.
As previously described, the connection between the RF link and the transmit is dynamically generated by a dynamic sub-array generator, which is essentially a programmable N RF :N TX And connecting to a network. The connection in the dynamic sub-array generator and the phase value of the phase shifter are both dependent on N TX ×N RF Order analog precoding matrix F RF To simulate the precoding matrix F RF Which in turn is directly related to the downlink channel information.
Suppose that a base station can obtain KXN through uplink and downlink reciprocity of a time division duplex system and user side feedback of a frequency division duplex system TX The rank downlink channel matrix H is expressed as
In the above-mentioned method, the step of,
(k＝1,2,...,K,n TX ＝1,2,...,N TX ) Indicating the nth base station TX Channel coefficients from the antenna to the kth receiving antenna, for>
And->
Respectively indicate->
Amplitude and phase of (a) are provided.
And the base station end completes the mixed precoding and implements the downlink transmission. Let the received signal-to-interference-and-noise ratio corresponding to the nth data stream be gamma n It can obtain a spectral efficiency of R n ＝E(log 2 (1+γ n ) The operator "E" here indicates mathematical expectations. The optimal design goal of the mixed pre-coding is that
Equation (2) is typically a joint non-convex optimization problem and does not yield an optimal solution. The invention will employ the following pair F RF And F BB A sub-optimal method of decoupling solution.
Under the constraint condition of mixed pre-coding based on a multi-connection structure and a dynamic subarray, the phase information of the channel coefficient is directly extracted to generate the phase shift value of the phase shifter corresponding to each antenna, which is essentially to the nth base station end through a certain criterion TX And selecting the most proper J antennas from candidate channel coefficients corresponding to all K receiving antennas, and extracting the phases of the J antennas. Through previous researches of the inventor, it is found that J near-optimal solutions with low complexity can be obtained by selecting J candidate channel coefficients with maximum amplitude from the K candidate channel coefficients corresponding to the receiving antennas.
In summary, the analog precoding method of the present invention is based on a large-scale MIMO with a multi-connection structure, in which each antenna can be connected to J radio frequency links, each radio frequency link can be connected to JM antennas, and the number of required phase shifters is j×n TX The method comprises the steps of carrying out a first treatment on the surface of the Wherein m=n TX /N RF ；N TX And N RF The number of transmitting antennas and the number of radio frequency links at the base station end are respectively.
Analog precoding matrix F RF Is N TX ×N RF The order block diagonal sparse matrix consists of Q-1 KMXK order submatrices and 1 (N) TX -(Q-1)KM)×(N RF The- (Q-1) K) order submatrices sequentially form the diagonal of the block, the rest elements are usually all set to zero, and the analog precoding matrix is solved only by solving each non-diagonalA sub-matrix of zero is sufficient.
The specific steps of the technical scheme (the algorithm of successively maximizing channel gain by transmitting antennas) used in the invention are as follows.
The amplitude and phase of each element of the input channel matrix H, i.e
And->
Is provided with->
Here, the operator->
Representation pair N RF and/K is rounded up.
Step 1: solving an analog precoding matrix F RF The first Q-1 submatrices of (a);
initial setting q=1
Step 101. Traversing the transmitting antenna
n TX Each antenna in= (q-1) km+1, (q-1) km+2, qKM, at the nth of the channel matrix H TX Column all K channel coefficients
J pieces with the largest amplitude are selected, and the corresponding receiving antenna serial numbers are recorded as
J is multiple connection factors of 1-N RF ；
Step 102, simulating a precoding matrix F RF Is the first of (2)
Individual elements
Wherein the method comprises the steps of
Representing the element +.>
Is a phase of (2);
step 103, if the channel coefficient corresponding to a certain receiving antenna is selected to JM times in the traversal process, deleting the channel coefficient from the candidate set in the subsequent selection process;
step 104, respectively making q=2, 3 and … Q-1; repeating steps 101-103;
step 2: solving an analog precoding matrix F RF Is the Q sub-matrix of (2);
Wherein the method comprises the steps of
Representing the element +.>
Is a phase of (2);
step 3, collecting all elements obtained in the step 1 and the step two, and combining to form an analog precoding matrix F RF 。
The analog precoding matrix F obtained by the above method RF Has the following characteristics:
nth (n) TX The row has J non-zero elements, the row dimension and the column dimension of which respectively correspond to the serial number n of the transmitting antenna TX The radio frequency link sequence number connected with the antenna, and the specific value of the radio frequency link sequence number depends on the construction result of the dynamic subarray. Nth (n) RF The columns have JM non-zero elements whose row dimensions correspond to those of the RF link n RF The number of the JM transmit antennas connected, the specific number of the JM transmit antennas depends on the dynamic sub-array construction result.
Modulo equality of all non-zero elements, indicating F RF Only phase transformation is involved, and can be achieved by a phase shifter.
The Frobenius norm of Fu Luo Beini is 1 for each column, indicating F RF The power of the signal is not changed.
In the case of a single user terminal, the digital precoding matrix is solved by singular value decomposition.
At this time, the parameter K corresponds to the number of antennas of the single receiver, and the number of independent data streams N is transmitted S Satisfy N S ≤K。
Step 3. Obtaining the analog precoding matrix F according to the present invention RF Thereafter, an equivalent channel matrix g=hf can be calculated RF . Then the singular value decomposition is carried out on G, namely
G＝UΣV H (4)
In the above formula, U, Σ, and V represent a left singular matrix, a singular value matrix, and a right singular matrix of G, respectively. Taking the front N of V S Columns, i.e. digital precoding matrix F BB ＝V(1:N S ). The total precoding matrix f=f can be verified RF F BB The Frobenius norms for each column are all 1, i.e. the total precoding process does not change the signal power.
Representing multiple data streams input to a hybrid precoder as vectors
At the moment of solving F RF And F BB Thereafter, the input-output relationship of the digital precoder and the analog precoder can be expressed as
The final output signal y is N TX The dimension vectors are respectively formed by N TX And transmitting by using the antenna.
Referring to fig. 3, the overall hybrid precoding spectrum efficiency performance of the inventive method is compared with existing full connection structure and partial connection structure methods by simulation. Wherein, the analog pre-coding link of the full-connection structure adopts literature [ Liang L, et al Low-complexity hybrid precoding in massive multiuser MIMO systems [ J ]]IEEE Wireless Communications Letters,2014,3 (6): 653-656 ] the digital precoding procedure employs singular value decomposition; the analog pre-coding link of the partial connection structure adopts literature [ Zhang Lei, etc. ] large-scale MIMO hybrid pre-coder and matching relation [ P ]]The method is described in ZL202010844421.8,2022-03-11, and the digital precoding link adopts singular value decomposition. The simulation conditions and main parameters are as follows: the channels obey Rayleigh fading, and the channels between all the receiving and transmitting antenna pairs are mutually independent; base station antenna number N TX Number of rf links n=128 RF 8, number of receive antennas k=8, number of independent data streams N S =8, multiple junction scale factor j=1, 2,4; the base station can obtain an accurate downlink channel matrix H. From this, it is seen that: when j=1, the method of the invention degenerates into a partial connection structure, but due to the adoption of a more advanced dynamic sub-array design, the spectral efficiency in the shown signal-to-noise ratio region is improved by about 12-30% compared with the existing partial connection structure + fixed sub-array and sequencing method; as J increases, the performance of the method is gradually improved; when j=4, the spectral efficiency of the method in the signal-to-noise ratio region shown can reach more than 95% of the existing full connection structure method, and the number of required phase shifters is only half of that of the method.
Example 2: in the case of a plurality of single-antenna user terminals, the digital precoding matrix is solved by zero forcing.
At this time, the parameter K corresponds to the total number of user terminals or the total number of receiving antennas, and the number of independent data streams N is transmitted S Satisfy N S =k. Corresponding digital precoding matrix F BB Can be calculated by
Wherein the equivalent channel matrix g=h×f RF The superscript H denotes the Hermitian transpose operation of the matrix F The Frobenius norm of the matrix is represented.
The total precoding matrix f=f can be verified RF F BB The Frobenius norms for each column are all 1, i.e. the total precoding process does not change the signal power.
Representing multiple data streams input to a hybrid precoder as vectors
At the moment of solving F RF And F BB Thereafter, the input-output relationship of the digital precoder and the analog precoder can be expressed as
The final output signal y is N TX The dimension vectors are respectively formed by N TX And transmitting by using the antenna.
See fig. 4. The overall mixed precoding spectrum efficiency performance of the method is compared with that of the existing full-connection structure and partial-connection structure through simulation. Wherein, the full connection structure adopts literature [ Liang L, et al Low-complexity hybrid precoding in massive multiuser MIMO systems [ J ]]IEEE Wireless Communications Letters,2014,3 (6): 653-656 ] method; the analog precoding link of the partial connection structure uses literature [ Zhang Lei, etc. ] Large-scale MIMO hybrid precoder and matching relationship [ P ]]ZL202010844421.8,2022-03-11. The simulation conditions and main parameters are as follows:the channels obey Rayleigh fading, and the channels between all the receiving and transmitting antenna pairs are mutually independent; base station antenna number N TX Number of rf links n=128 RF =8, the number of user terminals (total number of receive antennas) k=8, the multiple connection scale factor j=1, 2,4; the base station can obtain an accurate downlink channel matrix H. From this, it is seen that: when j=1, the method of the invention improves the spectral efficiency in the signal-to-noise ratio region by about 30-140% compared with the existing "partial connection structure+stator array and ordering" method; as J increases, the performance of the method is gradually improved; when j=4, the spectral efficiency of the method of the present invention in the signal-to-noise ratio region shown can reach more than 95% of the existing "fully connected structure" method, and the number of required phase shifters is only half of that of the latter.
Aiming at large-scale MIMO mixed precoding, the invention provides an analog precoding method based on a multi-connection structure. In the proposed multiple connection structure, each antenna can be connected to multiple radio frequency links, thereby enabling the analog precoding loop to save energy and utilize more antenna resources.
Further, based on the multi-connection structure, by utilizing the characteristic that the channel gains from different transmitting antennas to different receiving antennas are different, phase information of a plurality of channel coefficients with the largest amplitude is selected from the channel coefficients from each transmitting antenna to all receiving antennas to generate an analog precoding factor set corresponding to the transmitting antenna. Establishing a connection relation between each radio frequency link and a corresponding transmitting antenna according to the serial numbers of the receiving antennas corresponding to all the selected channel coefficients, thereby generating a corresponding dynamic subarray; and constructing an analog precoding matrix with a block diagonal sparse structure according to the analog precoding factor sets of all the transmitting antennas. In the digital pre-coding link, the invention is not limited to a specific method: the method comprises the steps of obtaining an equivalent channel matrix based on the product of an analog precoding matrix and an actual channel matrix, and carrying out common Singular Value Decomposition (SVD), zero Forcing (ZF) and other treatments on the equivalent channel matrix according to different situations. Finally, the original data stream is sequentially input into a designed digital precoder and an analog precoder for processing, and finally transmitted through an antenna.
The foregoing description of the preferred embodiments of the present invention is not obvious contradiction or on the premise of a certain preferred embodiment, but all the preferred embodiments can be used in any overlapped combination, and the embodiments and specific parameters in the embodiments are only for clearly describing the invention verification process of the inventor and are not intended to limit the scope of the invention, and the scope of the invention is still subject to the claims, and all equivalent structural changes made by applying the specification and the content of the drawings of the present invention are included in the scope of the invention.
Claims (4)
1. The large-scale MIMO analog precoding method based on the multi-connection structure is characterized by comprising the following steps of: the method comprises the following steps:
step 1: solving an analog precoding matrix F RF The first Q-1 submatrices of (a);
initially setting q=1;
step 101. Traversing the transmitting antenna
n TX Each antenna in= (q-1) km+1, (q-1) km+2, qKM, at the nth of the channel matrix H TX Column all K channel coefficients
J pieces with the largest amplitude are selected, and the corresponding receiving antenna serial numbers are recorded as
J is multiple connection factors of 1-N RF ；
Step 102, simulating a precoding matrix F RF Is the first of (2)
Individual elements
Wherein the method comprises the steps of
Representing the element +.>
Is a phase of (2);
step 103, if the channel coefficient corresponding to a certain receiving antenna is selected to JM times in the traversal process, deleting the channel coefficient from the candidate set in the subsequent selection process;
step 104, respectively making q=2, 3 and … Q-1; repeating steps 101-103;
step 2: solving an analog precoding matrix F RF Is the Q sub-matrix of (2);
step 201. For transmitting antenna n TX ＝(Q-1)KM+1，(Q-1)KM+2，...，N TX In the nth of the channel matrix H TX Front N of column RF - (Q-1) K channel coefficients
J pieces with the largest amplitude are selected, and the corresponding receiving antenna serial number is marked as +.>
Step 202, simulating a precoding matrix F RF Is the first of (2)
Individual elements
Wherein the method comprises the steps of
Representing the element +.>
Is a phase of (2);
step 203, in the above process, if the channel coefficient corresponding to a certain receiving antenna is selected for JM times, deleting the channel coefficient from the candidate set in the subsequent search;
step 3, collecting all elements obtained in the step 1 and the step two, and combining to form an analog precoding matrix F RF ；
The channel matrix
k is the number of receiving antennas, N TX And N RF The number of transmitting antennas and the number of radio frequency links at the base station end are respectively, and M=N TX /N RF The method comprises the steps of carrying out a first treatment on the surface of the JM is the number of antennas that each radio frequency link can connect.
2. The method for dynamic sub-array based analog precoding in massive MIMO according to claim 1, wherein the multiple connection factor j=1 or N RF 。
3. The large-scale MIMO hybrid precoding method based on the multi-connection structure is characterized by comprising the steps of calculating a digital precoding matrix, wherein the calculation method of the digital precoding matrix is any one of the following two methods:
method 1:
calculating an equivalent channel matrix g=hf RF ，
Performing singular value decomposition on G, i.e.
G＝UΣV H (2)
In the above description, U, Σ, and V represent a left singular matrix, a singular value matrix, and a right singular matrix of the equivalent channel matrix G, respectively, and the superscript H represents conjugate transpose of the matrices;
taking the front N of right singular matrix V S Columns, i.e. digital precoding matrix F BB ＝V(1:N S )，N S The number of independent data streams to be transmitted;
method 2:
digital precoding matrix
Wherein the equivalent channel matrix g=h×f RF H is a channel matrix, and the superscript H of G represents Hermitian transpose operation of the matrix F A friendship Luo Beini us (Frobenius) norm representing a matrix, K being the total number of receiving antennas;
h and F RF Channel matrix and analog precoding matrix according to claim 1 or 2, respectively.
4. A massive MIMO based on multiple connection structure, characterized by: each antenna may be connected to J RF links, each RF link may be connectedThe JM antennas are connected, and the required phase shifters are J.times.N TX ；
Wherein m=n TX /N RF ；N TX And N RF The number of transmitting antennas and the number of radio frequency links at the base station end are respectively.
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