CN108306664B - Method for generating parameterized block DFT codebook based on user distribution - Google Patents

Method for generating parameterized block DFT codebook based on user distribution Download PDF

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CN108306664B
CN108306664B CN201810095095.8A CN201810095095A CN108306664B CN 108306664 B CN108306664 B CN 108306664B CN 201810095095 A CN201810095095 A CN 201810095095A CN 108306664 B CN108306664 B CN 108306664B
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codebook
alpha
block
user
code word
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CN108306664A (en
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龙恳
陈琪
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Chongqing University of Post 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
    • H04B7/0413—MIMO systems
    • H04B7/0456—Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0413—MIMO systems
    • H04B7/0456—Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting
    • H04B7/0478—Special codebook structures directed to feedback optimisation

Abstract

Based onA method for generating a user distributed parameterized block DFT codebook belongs to the technical field of wireless communication. The method comprises the following steps: 1) for codebook WLCarrying out uneven blocking to obtain m blocking codebooks; 2) respectively introducing m variable phase parameters alpha and beta to construct a parameterization-based block codebook; 3) screening out the optimal variable phase parameter alpha according to the maximum average correlation of the channel matrix H and the code word wiAnd betai(ii) a 4) Generating alphaiAnd betaiThe parameter table of (1); 5) according to different user distribution conditions, determining one or more groups of code word resolution (alpha) corresponding to the parameter tablei,βi) One or more block codebooks configured; 6) for codeword resolution (α)i,βi) The formed block codebook is dynamically corrected. The method is suitable for large-scale MIMO limited feedback precoding systems under the condition of uniform distribution and non-uniform distribution of users, has certain performance improvement compared with the traditional DFT codebook and the LTE-A codebook, and has more obvious advantages along with the increase of the number of antennas.

Description

Method for generating parameterized block DFT codebook based on user distribution
Technical Field
The invention belongs to the technical field of wireless communication, and particularly relates to a method for generating a parameterized block DFT codebook based on user distribution.
Background
With the popularization of intellectualization, billions of intelligent devices need to realize wireless connection, and the wireless network capacity brings unprecedented challenges. The existing research shows that a Multi-user multiple-input multiple-output (MU-MIMO) system has a great potential in improving system capacity and Spectrum utilization (SE) by spatial diversity and scheduling multiple users on the same Resource Block (RB) according to channel conditions of different User Equipments (UEs). The precoding technique has been widely studied in academia as one of key techniques in MU-MIMO systems, and it eliminates inter-user interference (MUI) and inter-symbol interference (ISI) by obtaining accurate downlink Channel State Information (CSI), thereby ensuring system performance. In Time Division Duplex (TDD) systems, CSI can be obtained directly using channel reciprocity. However, in a Frequency Division Duplex (FDD) system, since the uplink and downlink channels operate in different frequency bands, CSI can only be obtained through the feedback link. Considering the limited bandwidth in the actual feedback link, it becomes especially important for the codebook-based precoding research with high capacity and low overhead.
When the base station is on the end of the dayWhen the number of linear array elements is limited, the corresponding channel coefficients are correlated. For Uniform Linear Arrays (ULA), the DFT codebook is a known codebook that approximately matches optimal beamforming. In the prior art, some codebook methods based on traditional DFT construction exist, for example, LTE-Advanced Release 10 adopts DFT matrix to construct codebook for effectively matching 32 uniform beams in space related channel, the technology is to divide space equally, and the codeword resolution is
Figure BDA0001564783080000011
The method is suitable for uniform distribution of users, but the code word resolution is too single and not flexible enough, and the uniform division of the space enables a dense area and a sparse area of the users to adopt the same code word resolution, so that the system performance is limited.
The patent "precoding method based on double codebooks in massive MIMO" (patent application number: 201610742843.8, publication number: CN106100712A) discloses a precoding method based on double codebooks, which comprises the following steps: (1) generating a first codebook, and selecting an optimal codeword of the first codebook; (2) expanding the column vector of the optimal code word of the first codebook to obtain a second codebook, and selecting the optimal code word of the second codebook; (3) comparing the singular values of the two codebooks; (4) selecting a precoding matrix and index information P from a first codebook; (5) selecting a precoding matrix and index information P from a second codebook; (6) the receiving end feeds back the optimal precoding matrix index information P to the transmitting end. According to the method, the codebook is generated for the first time to select the code words, then the code words are expanded into the second codebook to select the code words again, and finally feedback is performed. The patent "eight antenna codebook design method reusing LTE codebook" (patent application No. 201010293253.4, publication No. CN101958771A) provides an eight antenna design method reusing LTE codebook, which includes: based on a rotating DFT codebook. And generating an eight-antenna LTE-A codebook with the rank of 8. The invention maintains the backward compatibility of LTE-A, but only discusses the extension to eight antennas, and can not be directly used in a large-scale number of antenna arrays.
Disclosure of Invention
Based on the problems, the invention provides a method for generating a parameterized partitioned DFT codebook based on user distribution, which can be applied to a large-scale MIMO limited feedback system under non-uniform distribution. The method comprises the following steps:
1) for codebook W with feedback bit number LLCarrying out uneven blocking to obtain m blocking codebooks;
2) respectively introducing m variable phase parameters alpha and beta, denoted as alpha0,α1,...,ai,...,αm-1And beta0,β1,...,βi,...,βm-1Constructing a parameterization-based block codebook; where α represents the phase of the reference beam and β represents the phase separation of the adjacent beam from the first beam;
3) defining average correlation of channel matrix H and code word w, and screening out optimum variable phase parameter alpha according to maximum average correlationiAnd betai；
4) Generating screened alpha according to different antenna numbers, different feedback bit numbers and different user azimuth anglesiAnd betaiThe parameter table of (1);
5) according to different user distribution conditions, determining one or more groups of code word resolution (alpha) corresponding to the parameter tablei,βi) One or more block codebooks are formed.
Further, the codebook W with the number of feedback bits of LLThe specific method for obtaining m partitioned codebooks by carrying out uneven partitioning comprises the following steps:
codebook W with feedback bit number LLThe number of non-uniform feedback bits is l0,l1,...,lm-1The m block codebooks, then:
Figure BDA0001564783080000031
the intervals of adjacent code words in the m block codebooks are r0,r1,...,rm-1And r is0≠r1≠...≠rm-1Then, it is expressed as:
Figure BDA0001564783080000032
Figure BDA0001564783080000033
…
Figure BDA0001564783080000034
further, the block codebook construction method based on parameterization is as follows:
code book
Figure BDA0001564783080000035
The middle code word is as follows:
Figure BDA0001564783080000036
n0＝0,1,...,N0-1，
code book
Figure BDA0001564783080000037
The middle code word is as follows:
Figure BDA0001564783080000038
n1＝0,1,...,N1-1
…
code book
Figure BDA0001564783080000041
The middle code word is as follows:
Figure BDA0001564783080000042
nm-1＝0,1,...,Nm-1-1
then each partitioned codebook is generated as:
Figure BDA0001564783080000043
Figure BDA0001564783080000044
…
Figure BDA0001564783080000045
wherein, M represents the number of antennas adopted by the base station end; n represents the number of codewords in the codebook; n is a radical ofm-1Representing the number of codewords in the mth block codebook.
Further, the average correlation between the defined channel matrix H and the codeword w is:
Figure BDA0001564783080000046
wherein:
Figure BDA0001564783080000051
the normalized channel of single power is represented, and the meaning of the symbol of | · | | | is modular operation.
Further, screening out the optimal variable parameter alpha according to the maximum average correlationiAnd betaiThe specific method comprises the following steps:
Figure BDA0001564783080000052
α'i,β'irepresents optional all alpha and beta parameter phase values, w (alpha'i,β'i) Representing the code word to be screened, E [ ·]Indicating averaging.
Further, the differentThe user distribution condition determines to adopt one or more groups of code word resolution (alpha) corresponding to the parameter tablei,βi) The block codebook is composed of:
when the users are evenly distributed, the cells adopt the same group of code word resolution (alpha)i,βi) A single partitioned codebook of configurations;
when users are not uniformly distributed, the cell adopts a plurality of groups of different code word resolutions (alpha)i,βi) A plurality of block codebooks are formed.
Further, when the users are evenly distributed, the cells adopt the same code word resolution (alpha)i,βi) The specific method of the single partitioned codebook is as follows: determining the number of code words of the selected codebook according to the user density of the whole cell so as to determine the number of feedback bits, and searching a group (alpha) in a parameter table according to the specific values of the number of antennas and the azimuth angle of the useri,βi) Forming a block codebook.
Further, when the users are not uniformly distributed, a plurality of different code word resolutions (alpha) are adoptedi,βi) The specific method of the block codebook is as follows: dividing regions according to user density, determining number of code words of codebook selected by each region according to different user densities in different regions in the region to determine feedback bit number, and searching multiple groups (alpha) in parameter table according to specific values of antenna number and user azimuth anglei,βi) A plurality of block codebooks are formed.
Further, the method also comprises the step 6) of aiming at the code word resolution (alpha)i,βi) The formed block codebook is dynamically corrected.
Further, the resolution (α) for the code wordi,βi) The method for dynamically correcting all the formed partitioned codebooks comprises the following steps: a block codebook with a large number of code words and a large number of feedback is adopted in a region with high user density; a block codebook with smaller code word quantity and smaller feedback number is adopted in an area with small user density; when the user density changes, the user density is updated by (alpha)i,βi) The block codebook employed by the region is updated.
The beneficial technical effects of the invention are as follows: the method generates the codebook with flexible and variable resolution by adjusting and selecting the parameters of the optimal solution, so that the codebook has the maximum average correlation with a multi-dimensional channel matrix under the non-uniform distribution of users, the performance is improved compared with the codebook constructed in the traditional DFT mode when the azimuth angles of the users are different, the feedback bit numbers are different, and the performance is improved when the number of the antennas is different.
Drawings
FIG. 1 is a schematic flow diagram of the process of the present invention;
FIG. 2 is a block codebook based model of a limited feedback precoding system;
FIG. 3 is a schematic diagram of the density of the uniform distribution of users;
FIG. 4 is a schematic density diagram of a user in a non-uniform distribution state;
FIG. 5 is a diagram illustrating uniform partition of a codebook based on conventional DFT construction;
FIG. 6 is a diagram of non-uniform partitioning of a space based on a parameterized block codebook;
FIG. 7 is a parameter value for maximizing average correlation;
FIG. 8 is a graph comparing codebook performance at different user azimuths;
FIG. 9 is a graph of codebook performance for different numbers of feedback bits;
fig. 10 is a comparison of codebook performance when the number of antennas at the base station side is different.
Detailed Description
The following describes a multi-user limited feedback transmission method based on user distribution according to the present invention with reference to the accompanying drawings.
FIG. 1 is a flow chart of the method of the present invention, wherein the method first uses a codebook W with a feedback bit number LLObtaining m feedback bits with l respectively by non-uniform blocking0,l1,...,lm-1The partitioned codebook of (a), expressed as:
Figure BDA0001564783080000071
wherein the adjacent code word intervals in the m block codebooks are r respectively0,r1,...,rm-1And r is0≠r1≠...≠rm-1。
Then respectively introducing m variable phase parameters alpha and beta, which are recorded as alpha0,α1,...,ai,...,αm-1And beta0,β1,...,βi,...,βm-1A parameterised based block codebook is constructed, where α denotes the phase of the reference beam and β denotes the phase separation of the adjacent beam from the first beam.
Then, defining average correlation of channel matrix H and code word w, and screening out optimum variable parameter alpha according to maximum average correlationiAnd betai. The codeword resolution (alpha) of the codebook is used regardless of whether the users are uniformly distributed or non-uniformly distributedi,βi) The maximum average correlation of the channel matrix H and the codeword w is satisfied.
Then alpha is generated according to different antenna numbers, different feedback bit numbers and different user azimuth anglesiAnd betaiThe parameter table of (1). When the users are evenly distributed, the cells adopt the same code word resolution (alpha)i,βi) A single partitioned codebook of configurations; when users are not uniformly distributed, the cell adopts a plurality of groups of different code word resolutions (alpha)i,βi) And forming a partitioned codebook. The above codeword resolution (α)i,βi) The data is found in the parameter table according to the number of antennas, the number of feedback bits and the azimuth angle of the user. For codeword resolution (α)i,βi) The formed block codebook can be dynamically corrected.
Example 1
The invention focuses on the construction of a parameterized block codebook, before which a codebook W needs to be constructedLM unequally spaced block codebooks. For this, reference may be made to a model of a limited feedback precoding system in massive MIMO, as shown in fig. 2. Consider aMIMO system down-link with K users, base station has NtOne antenna, user k has Nr,kThe total number of antennas of all users is
Figure BDA0001564783080000072
CkAs to the number of information streams,
Figure BDA0001564783080000073
a pre-coding matrix is represented which,
Figure BDA0001564783080000074
a channel matrix representing user k, wherein the symbols
Figure BDA0001564783080000075
A complex set is represented.
Precoding matrix W in the above equationkIs a codebook WLL denotes the number of feedback bits, where WLIs a set of precoding matrices based on a rotated DFT.
A codebook WLThe number of non-uniform feedback bits is l0,l1,...,lm-1M small codebooks:
Figure BDA0001564783080000081
the intervals of adjacent code words in the m block codebooks are r0,r1,...,rm-1And r is0≠r1≠...≠rm-1It is produced in the following form:
Figure BDA0001564783080000082
Figure BDA0001564783080000083
…
Figure BDA0001564783080000084
example 2
The codebook W needs to be constructedLAnd after the m partitioned codebooks with unequal intervals, constructing a parameterized partitioned codebook. At this time, m variable phase parameters alpha are introduced0,α1,...,αi,...,αm-1And beta0,β1,...,βi,...,βm-1Where α denotes the phase of the reference beam and β denotes the phase separation of the adjacent beam from the first beam, based on a parameterized, partitioned DFT codebook
Figure BDA0001564783080000085
The structure is as follows:
code book
Figure BDA0001564783080000086
The middle code word is as follows:
Figure BDA0001564783080000087
n0＝0,1,...N0-1
code book
Figure BDA0001564783080000088
The middle code word is as follows:
Figure BDA0001564783080000089
n1＝0,1,...N1-1
…
code book
Figure BDA00015647830800000810
The middle code word is as follows:
Figure BDA0001564783080000091
nm-1＝0,1,...Nm-1-1
then each partitioned codebook is generated as:
Figure BDA0001564783080000092
Figure BDA0001564783080000094
…
Figure BDA0001564783080000093
wherein, M represents the number of antennas adopted by the base station end; n represents the number of codewords in the codebook; n is a radical ofm-1Representing the number of codewords in the mth block codebook.
Example 3
After a block codebook based on the parameters alpha and beta is constructed, alpha is generated according to different antenna numbers, different feedback bit numbers and different user azimuth anglesiAnd betaiAnd (4) a parameter table.
The above-mentioned phase parameter alphaiAnd betaiThe method is selected according to the maximum average correlation of the channel matrix H and the code word w, and the average correlation of the channel matrix H and the code word w is as follows:
Figure BDA0001564783080000101
in the above formula
Figure BDA0001564783080000102
The normalized channel of single power is represented, and the meaning of the symbol of | · | | | is modular operation.
(α) regardless of whether the users are uniformly distributed or non-uniformly distributedi,βi) The selection of (A) is to satisfy the maximum average correlation, namely:
Figure BDA0001564783080000103
α'i,β'irepresents optional all alpha and beta parameter phase values, w (alpha'i,β'i) Indicates the code words to be screened for,
e [. cndot. ] represents the averaging.
When the users are evenly distributed, the cells adopt the same group of code word resolution (alpha)i,βi) A single partitioned codebook of configurations; when users are not uniformly distributed, the cell adopts a plurality of groups of different code word resolutions (alpha)i,βi) A plurality of block codebooks are formed.
For the case of uniform distribution of users, as shown in fig. 3, it can be described by uniform SPPP (Spatial Poisson Point Process). The method is generally applied to position distribution modeling of a base station, uniform distribution scenes of users and the like. Assuming that the radius of a cell is R, the azimuth angle of a user of a single user is phi, the area of the cell is A, and the number K of users in the cell obeys spatial Poisson point distribution K-Poisson (lambda A) with the intensity value of lambda, according to the property of Poisson distribution, the method comprises the following steps:
E[K]＝λ|A|
the probability of K users in the cell can be expressed as:
Figure BDA0001564783080000104
the single poisson distribution reflects the uniform distribution of users, and considering the position specificity of the users, the uniform SPPP process hardly reflects the non-uniform distribution scene of the users, and ignores hot spot coverage areas such as office buildings, shopping malls and the like, and when the hot spot areas are concentrated in a certain sector or a certain azimuth angle interval, the users are in non-uniform distribution, for example, as shown in FIG. 4, the hot spot areas are mainly concentrated in azimuth angles of [ -45 degrees, 45 degrees °]Within the range of (1). To describe this non-uniform distribution characteristic, a user probability density function f is introduced hereden(φ)：
Figure BDA0001564783080000111
Then the probability that the user falls in the area is:
Figure BDA0001564783080000112
v is an exponential factor and C is a normalization factor that gives a probability of a user falling within a cell of 1.
In fig. 3, when the exponential factor v is 1, the cell users are uniformly distributed. In fig. 4, the users in the sparse area are uniformly distributed, and v is 1; the dense region index factor is v 0.01.
For uniform distribution of users as shown in fig. 3, the same codeword resolution (α) satisfying the maximum average correlation is adopted for the entire celli,βi) A single codebook is constructed. As shown in fig. 5, if the horizontal dimension space is represented by a unit circle, when N is N0When, the representation divides the space into N0Then referring to the number of base station side antennas, selecting the optimal same code word resolution (alpha) of the current formed codebook from the parameter table0,β0)。
For the user non-uniform distribution as shown in fig. 4, multiple groups are adopted to satisfy different codeword resolutions (alpha)i,βi) And forming a partitioned codebook. Screened by maximum average correlation (. alpha.)i,βi) Optimum parameter value because the number of codewords N is 2 by increasing the number of feedback bits LLIn addition, the parameter-based partitioned DFT codebook can be applied to a system with a large-scale antenna array.
The invention is directed to codeword resolution (alpha)i,βi) The formed block codebook can be dynamically corrected, namely, the block codebook with a large number of feedback numbers and a large number of codewords is used in a region with large user density; and the block codebook with smaller code word quantity and smaller feedback number is used in the area with small user density. Therefore, when the user density changes, the (alpha) is updatedi,βi) The block codebook is updated.
Because of its flexible beam resolutionBy imparting a specific alphai,βiAnd generating small codebooks of different codeword resolutions to adapt to the user non-uniform distribution scene under multiple antennas. For example, for a non-uniform distribution as shown in FIG. 4, the dense region may take the codeword as w1(α1,β1) The number of the code words is
Figure BDA0001564783080000121
The sparse region may adopt a codeword of w2(α2,β2) The number of the code words is
Figure BDA0001564783080000122
Codebook of l1>l2Due to N1>N2The dense area has a large number of code words using the codebook, and the interval of the code words is smaller, so the resolution ratio is high, and the sparse area has a small number of code words using the codebook, and the interval of the code words is larger, so the resolution ratio is low. The parameterization-based block codebook application under the non-uniform distribution shown in FIG. 4 is shown in FIG. 6.
The effectiveness of the parameterized DFT codebook can be verified by a multi-antenna MIMO system under an SCM channel, wherein an SCM model is proposed by a 3GPP combined with a joint Ad-Group of 3GPP2, and a common reference is formed for evaluating different outdoor MIMO environments. When an SCM (Single chip multiple Access) Urban Macrocell scene is adopted, the base station adopts an ULA (ultra wideband) cross-polarized antenna with the antenna number M being 4, the user side adopts a polarized antenna with the antenna number U being 1, and the cluster number N isclusterNumber of sub-diameters N per cluster ═ 6pathAt 20, the optimal solution is solved for the parameters in the parameterized DFT block codebook. When the number of feedback bits L is 2,3,4, and 5 and the number of code words N is 4,8,16, and 32, respectively, the corresponding (α) can be obtained1,β1)(α2,β2)(α3,β3)(α4,β4) Four sets of optimal solutions.
Solving the maximum average correlation according to the above formula at different user azimuthsAnd obtaining the optimal alpha and beta values in a traversing searching mode. Fig. 7 shows a table of parameters for the antenna number M of 4 and the feedback bit number L of 2,3,4,5, and it can be seen that the user azimuth angle phi is from 0 deg. to 60 deg., and the optimum angle alpha is1,α2,α3,α4Is approximated by four lines of similar slope, and beta1,β2,β3,β4The four straight lines with almost the same slope indicate that when the number of base station antennas is M equal to 4, the number of codewords has a significant effect on the value of α and a small effect on the value of β. And, as the azimuth angle of the user increases, the value of alpha increases approximately linearly, and the value of beta does not change approximately. Through the experimental statistics mode, the optimal parameter values of any number of antennas, any feedback bit number and any user azimuth angle can be obtained, and the DFT codebook with the maximum average correlation with the channel matrix can be obtained.
Simulation results and analysis
To evaluate the performance of the proposed variable parameter based partitioned DFT codebook, some key parameters of the simulation are shown in table 1.
TABLE 1 simulation parameters
Figure BDA0001564783080000131
Fig. 8 compares three codebooks (LTE-a codebook, DFT codebook, and DFT codebook based on parameterization), and codebook performance at different user azimuths when the number of antennas M of the base station is 4 and the number of codewords N is 4. It can be seen that as the user azimuth phi increases from 0 deg. to 60 deg., the LTE-a codebook performance decreases monotonically, while the DFT codebook performance based on parameterization increases monotonically, with mu being at most 0.84 at phi 60 deg.. The conventional DFT codebook performance is intermediate but not stable.
Fig. 9 compares the performance of three different codebooks with different feedback bit numbers when the number of antennas of the base station is M-4, and it can be seen from the simulation result that when the number of feedback bits L is 1, 2,3,4, i.e. the number of codewords N corresponds to 2, 4,8,16, the performance of the parameterized codebook is stable and slightly increased, whereas the performance of the conventional DFT codebook is poor when the number of feedback bits is low and good when the number of feedback bits is high, which is close to the performance of the parameterized DFT codebook. This is because the parameterized codebook employs a flexible and variable codeword resolution, and a codebook with the best performance can be selected no matter the number of feedback bits is large or small.
As can be seen from fig. 10, when the number of codewords is N ═ 32, the number of antennas at the base station increases, the dimension of the channel matrix increases, because the parameterized DFT codebook screens out the codebook with the largest average correlation with the channel matrix through traversal loop, and the conventional DFT codebook neglects the consideration of correlation, the codebook performance proposed by the present invention is superior to the conventional DFT codebook, and this advantage is more obvious when the number of antennas is larger, and is suitable for the multi-user MIMO system with large-scale antennas under non-uniform distribution of users.
Those skilled in the art will appreciate that all or part of the steps in the methods of the above embodiments may be implemented by associated hardware instructed by a program, which may be stored in a computer-readable storage medium, and the storage medium may include: ROM, RAM, magnetic or optical disks, and the like.
The above-mentioned embodiments, which further illustrate the objects, technical solutions and advantages of the present invention, should be understood that the above-mentioned embodiments are only preferred embodiments of the present invention, and should not be construed as limiting the present invention, and any modifications, equivalents, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (9)

1. A method for generating a parameterized block DFT codebook based on user distribution is characterized by comprising the following steps:
1) for codebook W with feedback bit number LLCarrying out uneven blocking to obtain m blocking codebooks;
2) respectively introducing m variable phase parameters alpha and beta, denoted as alpha0，α1，...，αi，...，αm-1And beta0，β1，...，βi，...，βm-1To construct parameterization-based partitionsA codebook; where α represents the phase of the reference beam and β represents the phase separation of the adjacent beam from the first beam;
3) defining average correlation of channel matrix H and code word w, and screening out optimum variable phase parameter alpha according to maximum average correlationiAnd betai；
4) Generating screened alpha according to different antenna numbers, different feedback bit numbers and different user azimuth anglesiAnd betaiThe parameter table of (1);
5) according to different user distribution conditions, determining one or more groups of code word resolution (alpha) corresponding to the parameter tablei，βi) One or more block codebooks configured;
the codebook W with the feedback bit number LLThe specific method for obtaining m partitioned codebooks by carrying out uneven partitioning comprises the following steps:
codebook W with feedback bit number LLThe number of non-uniform feedback bits is l0，l1，...，lm-1The m block codebooks, then:
Figure FDA0002766719430000011
the intervals of adjacent code words in the m block codebooks are r0，r1，...，rm-1And r is0≠r1≠…≠rm-1Then, it is expressed as:
Figure FDA0002766719430000012
Figure FDA0002766719430000013
…
Figure FDA0002766719430000014
2. the method for generating the DFT codebook based on user distribution as claimed in claim 1, wherein the method for constructing the DFT codebook based on parameterization is as follows:
code book
Figure FDA0002766719430000021
The middle code word is as follows:
Figure FDA0002766719430000022
n0＝0，1，...，N0-1，
code book
Figure FDA0002766719430000023
The middle code word is as follows:
Figure FDA0002766719430000024
n1＝0，1，...，N1-1
…
code book
Figure FDA0002766719430000025
The middle code word is as follows:
Figure FDA0002766719430000026
nm-1＝0，1，...，Nm-1-1
then each partitioned codebook is generated as:
Figure FDA0002766719430000027
Figure FDA0002766719430000028
…
Figure FDA0002766719430000031
wherein, M represents the number of antennas adopted by the base station end; n represents the number of codewords in the codebook; n is a radical ofm-1Representing the number of codewords in the mth block codebook.
3. The method for generating the user distribution based parameterized block DFT codebook according to any of the claims 1-2, wherein the average correlation between the defined channel matrix H and the code words w is:
Figure FDA0002766719430000032
wherein:
Figure FDA0002766719430000033
the normalized channel of single power is represented, and the meaning of the symbol of | · | | | is modular operation.
4. The method for generating the DFT codebook based on user distribution as claimed in claim 3, wherein the method selects the optimal variable parameter α according to the maximum average correlationiAnd betaiThe specific method comprises the following steps:
Figure FDA0002766719430000034
α′i，β′irepresents optional all alpha and beta parameter phase values, w (alpha'i，β′i) Representing the code word to be screened, E [ ·]Indicating averaging.
5. The method of claim 1, wherein the decision to adopt one or more sets of codeword resolutions (α) in the parameter table is determined according to different user distributionsi，βi) The block codebook is composed of:
when the users are evenly distributed, the cells adopt the same group of code word resolution (alpha)i，βi) A single partitioned codebook of configurations;
when users are not uniformly distributed, the cell adopts a plurality of groups of different code word resolutions (alpha)i，βi) A plurality of block codebooks are formed.
6. The method of claim 5, wherein when the users are distributed uniformly, the cells use the same codeword resolution (α)i，βi) The specific method of the single partitioned codebook is as follows: determining the number of code words of the selected codebook according to the user density of the whole cell so as to determine the number of feedback bits, and searching a group (alpha) in a parameter table according to the specific values of the number of antennas and the azimuth angle of the useri，βi) Forming a block codebook.
7. The method for generating the user distribution based parameterized block DFT codebook according to claim 5, wherein when the users are not uniformly distributed, a plurality of different codeword resolutions (α) are adoptedi，βi) The specific method of the block codebook is as follows: dividing regions according to user density, determining number of code words of codebook selected by each region according to different user densities in different regions in the region to determine feedback bit number, and searching multiple groups (alpha) in parameter table according to specific values of antenna number and user azimuth anglei，βi) A plurality of block codebooks are formed.
8. The method for generating the user distribution based parameterized block DFT codebook according to claim 1, further comprising step 6) for codeword resolution (α)i，βi) The formed block codebook is dynamically corrected.
9. The method of claim 8, wherein the resolution (α) for code word is determined by the DFT codebook generation methodi，βi) The method for dynamically correcting all the formed partitioned codebooks comprises the following steps: a block codebook with a large number of code words and a large number of feedback is adopted in a region with high user density; a block codebook with smaller code word quantity and smaller feedback number is adopted in an area with small user density; when the user density changes, the user density is updated by (alpha)i，βi) The block codebook employed by the region is updated.
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