Communication codebook design method, system and device

Abstract

The invention discloses a method, a system and a device for designing a communication codebook, belongs to the technical field of communication, and particularly relates to the field of codebook design in the field of communication. The communication system codebook is formed according to the following mode: # imgabs0 # wherein the lth column vector of # imgabs1 # matrix B is # imgabs2 # wherein a set C comprises index pairs (k1, k2) formed by J indexes of first dimensions and second dimensions, and # imgabs3 #

Description

Technical Field

[0001] The present application discloses a method, system and device for designing a communication codebook, which belongs to the field of communication technology, and particularly to the field of codebook design in the communication field. Background Art

[0002] In the codebook design of the 5G communication system, it is assumed that the terminal device is in the far field area of ​​the base station radiation wave. Under the far field condition, the propagation of electromagnetic signals follows the plane wave assumption. Under the plane wave assumption, the phase of the channel response shows a linear relationship between antennas. Therefore, the DFT vector in formula (2) can be used to characterize the channel guidance. As the number of base station antennas increases, the Rayleigh distance can reach hundreds of meters. At this time, it should be considered Figure 2 The phase of the channel response no longer presents a linear relationship between the antennas. Using DFT vectors to describe the channel steering vectors will inevitably cause serious performance loss. Summary of the invention

[0003] In order to solve the codebook design problem of overcoming the near-field effect under ultra-large-scale antenna arrays, this application improves W based on the traditional high-precision codebook. 1 Each vector b in the matrix l The codebook designed by the method of the present application has better adaptability and can be converted between near field and far field.

[0004] The present invention solves the above technical problems through the following technical solutions:

[0005] A method for designing a communication codebook, wherein the communication system codebook is constructed in the following manner:

[0006]

[0007] in, Matrix W 1 The dimension is 2N 1 N 2 ×2L, where N 1 and N 2 Respectively represent the number of antenna ports in the first dimension and the number of antenna ports in the second dimension in each polarization direction; the matrix B contains L column vectors, where L ≥ 1, and the lth column vector of the matrix B is:

[0008]

[0009] The set C contains index pairs consisting of J indexes of the first dimension and the second dimension (k 1 ,k 2 ),in represents the Kronecker product operation, and It is expressed as:

[0010]

[0011] O is an integer greater than or equal to 1, indicating the oversampling multiple of the IDFT / DFT vector, 0≤k 1 <ON 1 , 0≤k 2 <ON 2 ;

[0012]

[0013] in, N 1 is the number of antennas in the first dimension at the base station, d 1 is the spacing between adjacent antennas in the first dimension, N 2 is the number of antennas in the second dimension at the base station, d 2 is the distance between adjacent antennas in the second dimension, and λ is the wavelength of the reference subcarrier.

[0014] Further, the communication terminal reports J (k 1 ,k 2 ), To determine 1 b l ,in, Quantized as H in the range of 0 to 1 x , H y , H z value, by reporting the integer h x ∈{0,H x -1}、h y ∈{0,H y -1}、h z ∈{0,H z -1} to determine and

[0015] Further, W 2 Each element of is a complex number and is fed back to the base station in the form of amplitude and phase.

[0016] Further, determine each b l The J (k 1 ,k 2 ), Broadband reporting means that for each b l , the whole system bandwidth reports a group of J (k 1 ,k 2 ),

[0017] Further, the wavelength λ of the reference subcarrier is a wavelength corresponding to a central frequency point of a subband to which the codebook W is applied, and the subband includes M subcarriers, where M is an integer greater than or equal to 1.

[0018] On the basis of the above technical solution, the present application also applies the codebook designed by the communication system codebook design method using three-dimensional coordinates to the communication system and device.

[0019] The present application discloses a design method for a communication codebook, which has the following advantages: adapting to ultra-large-scale antenna arrays, whether the communication terminal is in the far field or near field, the corresponding channel can be matched by selecting different codebooks. For example, when the antenna terminal is in the far field, J=1 can be selected, and the codebook falls back to the traditional 5G codebook. When the communication terminal is in the near field, J>1 can be selected to adapt to different distances. It can be seen that the codebook has super strong scene adaptability. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a schematic diagram of a plane wave;

[0021] Figure 2 Schematic diagram of spherical wave;

[0022] Figure 3 Schematic diagram of spherical wave distance. DETAILED DESCRIPTION

[0023] The following embodiments, in conjunction with the accompanying drawings, are only intended to illustrate the technical solutions described in the claims and are not intended to limit the protection scope of the claims.

[0024] Massive Multiple-Input Multiple-Output (Massive MIMO) antenna systems have become a reality in 5G wireless communication networks, where base station equipment is equipped with 16 or 32 antennas. In order to obtain beamforming gain, the 3GPP standardization organization has designed a high-precision codebook for 5G's Massive MIMO antennas, where the precoding matrix W can be expressed as:

[0025]

[0026] Where W 1 Describes the long-term, broadband characteristics of the channel, including a DFT beam group; W 2 Describes the short-term, sub-band characteristics of the channel. 1 The structure is:

[0027]

[0028] Where B = [b 0 ,…,b L-1 ] is a matrix consisting of L oversampled DFT vectors. 1 The two diagonal blocks of are for two polarization directions respectively. Here, it is considered that the DFT beam groups of the two polarization directions are the same, that is, the same DFT beam is used for the two polarization directions. From its structure, W 1 The role of is to determine a set of DFT beams, and W 2 The function of W is to linearly combine the DFT beams. 2 The elements in are complex numbers and are fed back in the form of amplitude and phase. Assuming that the base station has 2N transmitting antennas, each polarization direction contains N antennas, and there are a total of ON DFT beams in the beam set, where O is an integer greater than or equal to 1, indicating the oversampling multiple. Then the m+1th DFT beam can be expressed as:

[0029]

[0030] Where m = 0, 1, 2,…, ON-1.

[0031] Matrix B is a matrix consisting of L beam vectors selected from ON DFT beams.

[0032] W 2 The dimension of is 2L×R, and its elements are:

[0033]

[0034] Among them, p l,r is a real number, 0≤p l,r ≤1, 1≤l≤2L,1≤r≤R.

[0035] Looking forward to the 6G mobile communication system, the application of higher frequency bands such as millimeter waves and terahertz will further reduce the size of antennas, which means that the scale of array antennas is expected to expand further. In future 6G base stations, there may be 256 or even more antennas, namely extremely large-scale antenna arrays (ELAA), which will lead to a rapid expansion of the near-field area of ​​the array. In the near-field area, the propagation of electromagnetic waves no longer follows the assumption of far-field plane waves, but exhibits the characteristics of spherical waves. Therefore, the near-field characteristics have become a new issue worthy of attention in the study of 6GELAA.

[0036] In the codebook design of the 5G communication system, it is assumed that the terminal device is in the far field area of ​​the radio waves radiated by the base station. The boundary between the so-called far field and near field is usually defined as the Rayleigh Distance, which is expressed as Where D represents the array aperture of the base station equipment, that is, the maximum size of the antenna array, and λ represents the wavelength. Usually, the location of the terminal device is far beyond the Rayleigh distance of the antenna array and is considered to be the far field, otherwise it is the near field.

[0037] Under far-field conditions, the propagation of electromagnetic signals follows the plane wave assumption, such as Figure 1 As shown; Under the assumption of plane wave, the steering vector of the antenna array can be expressed as

[0038]

[0039] Under the assumption of plane waves, the phase of the channel response presents a linear relationship between antennas. Therefore, the DFT vector in formula (2) can be used to characterize the channel steering quantity.

[0040] As the number of base station antennas increases, the Rayleigh distance can reach several hundred meters. At this time, we should consider Figure 2 Spherical waves;

[0041] The steering vector for this channel should be expressed as:

[0042]

[0043] The phase of the channel response no longer presents a linear relationship between antennas, and using the DFT vector to characterize the channel steering vector will inevitably cause serious performance loss. Specifically, under far-field conditions, the phase of the channel response changes linearly between antennas, and the phase of the DFT vector also changes linearly, so the DFT vector matches the channel response under far-field conditions.

[0044] However, under near-field conditions, the phases of the channels are no longer linear between antennas, so the original DFT vector is no longer suitable for near-field conditions.

[0045] In the current 5G communication system, and even in the future 6G transmission system, the base station is often equipped with a dual-polarization antenna array, such as a +45° polarization array and a -45° polarization array. Each polarization array contains N antenna elements. In the traditional codebook design, W = W 1 W 2 ,in, B is an N×L matrix, where each column of B is a DFT vector. In traditional communication systems, the end user is in the far field of the electromagnetic radiation field of the base station. Therefore, a DFT vector can point the beam in a specific direction. Considering the multipath components of the channel in the wireless communication system, the direction of each multipath is different. Therefore, the matrix B contains L DFT vectors to indicate the direction of each multipath. The end user reports the DFT vector number to the base station so that the base station user obtains the DFT vector selected by the end user, thereby constructing W1 However, under near-field conditions, a single DFT vector cannot point the beam in a specific direction. The following invention mainly solves the feedback and construction problems of B in the traditional codebook, specifically, how to determine each column vector of B.

[0046] Assume that, in three-dimensional coordinates, the coordinates of the communication terminal are (x u ,y u ,z u ). The base station antenna has two polarization directions, each of which contains N = N 1 ×N 2 antennas, located in the plane z = 0. In the x-axis direction (also called the first dimension), there are N 1 antennas, and the interval between adjacent antennas is d 1 , there are N in the y-axis direction (also called the second dimension) 2 antennas, and the interval between adjacent antennas is d 2 , so the nth 1 Column No. n 2 The position coordinates of the row antenna are ((n 1 -1)×d 1 ,(n 2 -1)×d 2 ,0), such as Figure 3 As shown; Based on the above assumptions, the communication terminal to the base station 1 Column No. n 2 Distance between antennas It can be expressed as:

[0047]

[0048] Correspondingly, the steering matrix A of the antenna array from the communication terminal to the base station can be obtained.

[0049]

[0050] in,

[0051]

[0052] The purpose of the present invention is to enable the base station to obtain the steering matrix A through feedback of certain parameters by the terminal.

[0053] The matrix A is subjected to a two-dimensional discrete Fourier transform to obtain the matrix D. The so-called two-dimensional discrete Fourier transform is to perform a discrete Fourier transform on each row of the matrix A, and then perform a discrete Fourier transform on each column of the obtained matrix, that is,

[0054]

[0055] in, is the kth 1 Column k 2 Elements of a row.

[0056] Using the phase principle, for When the value is larger, It can be expressed as

[0057]

[0058] in, Indicates the amplitude, k 1 , k 2 Represents the sample index of the first dimension and the second dimension after the two-dimensional DFT transformation. Assume that there are J larger sample values, that is, Where T is the set threshold, and the index pairs of J sample values ​​form a set C, that is, (k 1 ,k 2 )∈C. Then, omitting Small value, the steering matrix A can be expressed as

[0059]

[0060] in,

[0061]

[0062]

[0063] is the DFT vector of the first and second dimensions. Note that if the matrix A is vectorized, that is, each column of A is listed together to form a long vector a, then

[0064]

[0065] Where a is N 1 N 2 ×1 vector, Represents the Kronecker product operation.

[0066] It should be noted that under ideal far-field conditions, only one element in the two-dimensional DFT transform D of the steering matrix A is non-zero. However, under near-field conditions, there will be multiple non-zero elements in D. If the communication terminal sends J (k 1 ,k 2 ) and J coefficients Feedback is given to the base station, and the base station can then construct the steering vector a.

[0067] Below, we mainly focus on J Generally speaking, J Amplitude The difference is not big. If we set J is a constant, that is (k 1 ,k 2 )∈C, which has little impact on performance, where P is a constant determined by the base station transmission power, so there is no need for feedback And for Phase

[0068]

[0069] Among them l r Only related to the wavelength of the carrier frequency, l 1 and l 2 The first dimension of the antenna aperture (N 1 d 1 ) and the second dimension of the antenna aperture (N 2 d 2 ), the wavelength of the carrier frequency and the antenna aperture are both known quantities and do not require feedback. The communication terminal only needs to feedback x u ,y u and z u , and k 1 and k 2 You can determine phase.

[0070] It should be noted that due to

[0071] but The phase can be further expressed as

[0072]

[0073] You can as well as If feedback is given, the value range can be set to 0 to 1.

[0074] Based on the above analysis, the present invention provides a codebook design method for ultra-large-scale arrays:

[0075] The precoding matrix is ​​composed of the following formula:

[0076]

[0077] Where W 1 The structure is

[0078]

[0079] Where B = [b 0 ,…,b L-1 ] is composed of L N 1N 2 ×1 vector. Vector b l It can be expressed as

[0080]

[0081] in represents the Kronecker product operation, and It is expressed as:

[0082]

[0083] Note that O represents the oversampling multiple of the DFT vector. When O>1, the granularity of the DFT vector can be improved. 0≤k 1 <ON 1 , 0≤k 2 <ON 2 .

[0084]

[0085] make as well as Then the above formula can be rewritten as:

[0086]

[0087] The communication terminal reports J (k 1 ,k 2 ) Yes, and and To determine b l .

[0088] It should be noted that in a multi-carrier system, the system bandwidth is composed of several subcarriers. Here, it is assumed that M subcarriers constitute a subband, and the subcarrier frequencies are f, f+Δf, f+2Δf, …, f+(M-1)Δf, where Δf is the subcarrier spacing. The terminal user can report only the parameters corresponding to one subcarrier (such as the center subcarrier) (J (k 1 ,k 2 ) for, and the normalized x u ,y u ,z u ,Right now and ), the base station can infer the parameters corresponding to the remaining subcarriers according to the subcarrier spacing, and thus calculate the b of the remaining subcarriers. l .

[0089] The rest of the construction and feedback methods of the precoding matrix are the same as the traditional method. For example, the matrix W 2 The dimension is 2L×R, where W 2Each element of is a complex number and is fed back to the base station in the form of amplitude and phase.

[0090] The communication system codebook design method is applied in a communication system and a device.

[0091] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for designing a communication codebook, characterized in that: The communication system codebook is constructed as follows: in, The dimension of the matrix W1 is 2N1N2×2L, where N1 and N2 represent the number of first-dimensional antenna ports and the number of second-dimensional antenna ports in each polarization direction, respectively; the matrix B contains L column vectors, where L≥1, and the l-th column vector of the matrix B is: The set C contains index pairs (k1, k2) consisting of J indexes of the first dimension and the second dimension, where represents the Kronecker product operation, and It is expressed as: 0 is an integer greater than or equal to 1, indicating the oversampling multiple of the IDFT vector, 0≤k1<ON1, 0≤k2<ON2; in, d1 is the distance between adjacent antennas in the first dimension, d2 is the distance between adjacent antennas in the second dimension, and λ is the wavelength of the reference subcarrier.

2. The method for designing a communication codebook according to claim 1, characterized in that: The communication terminal reports J (k1, k2), To determine 1 b l ,in, Quantized as H in the range of 0 to 1 x , H y , H z value, by reporting the integer h x ∈{0,H x -1}、h y ∈{0,H y -1}、h z ∈{0,H z -1} to determine and 3. The method for designing a communication codebook according to claim 1, characterized in that: Each element of W2 is a complex number and is fed back to the base station in the form of amplitude and phase.

4. The method for designing a communication codebook according to claim 1, characterized in that: Determine each b l J (k1, k2), Broadband reporting means that for each b l , the whole system bandwidth reports a group of J (k1, k2), 5. The design method of the communication codebook according to claim 1 is characterized in that the wavelength λ of the reference subcarrier is the wavelength corresponding to the center frequency point of the subband to which the codebook W is applied, and the subband includes M group carriers, where M is an integer greater than or equal to 1.

6. A system using the communication codebook design method according to any one of claims 1 to 5, characterized in that: The system uses a codebook designed by the method described in any one of claims 1 to 5.

7. A device using the communication codebook design method according to any one of claims 1 to 5, characterized in that: The communication device uses a codebook designed by the method described in any one of claims 1 to 5.

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