A massive MIMO precoding grouping method for satellite communications

Abstract

The present invention discloses a large-scale MIMO precoding grouping method for satellite communication. The method comprises the following steps: Step S1: Obtain the location information of large-scale users and calculate the channel vector. Step S2: The transmitting end uses the channel vector of the user to select the user by using the principle of minimizing the beam gain and the nearest user orthogonal position. A user index is selected in each iteration to satisfy the minimum weighted sum of the channel vector norm, the beam gain and the orthogonal position distance, and the allocated user set is obtained to form a radio frequency link that can send a transmission signal. Step S3: Use the time division multiplexing multi-beam communication method to communicate. Compared with the prior art, the present invention solves the problem of the communication effectiveness of a single satellite for large-scale user communications and improves the communication rate and stability.

Description

Technical Field

[0001] The invention belongs to the field of communication, and in particular relates to a large-scale MIMO precoding grouping method for satellite communication. Background Art

[0002] Satellite communications, like terrestrial communications, are carried out by transmitting and receiving radio waves. Phased array antennas can be used in multiple-input multiple-output (MIMO) scenarios, receiving signals from multiple users at the same time and sending multiple signals to users at specific locations simultaneously through multi-beam technology. In a phased array, the device that controls the amplitude and phase of each small antenna element is called a beamforming network. The beamforming network uses the given user position and the signal to be sent to each user, and based on the known phased array data, such as the number and arrangement of phased array units, calculates the parameters of each phased array unit through optical and electromagnetic principles.

[0003] With the rapid increase in user demand, a satellite will serve a large number of users at the same time, and the signals sent by the same number of users at the same frequency will cause co-frequency interference. At the same time, the increase in the number of users also means the increase in beams. If the antenna parameters remain unchanged, the calculation efficiency and operation efficiency of precoding will decrease. Summary of the invention

[0004] The purpose of the present invention is to provide a large-scale MIMO precoding grouping method for satellite communications to solve the technical problem that with the rapid increase in user demand, the number of users served by a satellite at the same time will be very large, and the signals sent simultaneously at the same frequency by the users will have co-frequency interference. At the same time, the increase in the number of users also means an increase in beams. When the antenna parameters remain unchanged, the calculation efficiency and operation efficiency of precoding will be reduced.

[0005] In order to solve the above technical problems, the specific technical solutions of the present invention are as follows:

[0006] A large-scale MIMO precoding grouping method for satellite communication comprises the following steps:

[0007] S1: Establish a phased array model. The phased array has M v ×M u There are K antenna elements arranged in a matrix with a distance between the elements equal to half the transmission wavelength. There are K users who need to communicate. In an area, the elevation and azimuth angles of existing users with respect to the satellite are determined based on their positions, and the channel vectors of the users are measured.

[0008] S2: The transmitter uses the user's channel vector and the principle of minimizing beam gain and the closest user orthogonal position to select users. In each iteration, a user index is selected to minimize the weighted sum of the channel vector norm, beam gain, and orthogonal position distance. The assigned user set is obtained to form a radio frequency link for sending transmission signals.

[0009] S3: Communicate using time division multiplexing multi-beam communication method.

[0010] Furthermore, the beam gain method used in S2 uses the signal-to-noise ratio of a single user's beam under a phased array to another user's beam to measure the correlation between users. The method of minimizing the user's orthogonal position uses a discrete Fourier transform matrix to calculate the user's orthogonal position, and uses the distance between the user and the nearest orthogonal position to measure the correlation between users. Minimizing the user's orthogonal position ensures that the beam pointing to each user individually does not cover other users in the same group, thereby reducing interference between users after precoding.

[0011] Furthermore, S2 specifically includes the following steps:

[0012] S2.1: For each user numbered k, its pitch angle θ k , the azimuth is φ k , use the following formula to transfer to the coordinate point (u k , v k ), where u k , v k It represents the horizontal and vertical coordinates in this space and is calculated using the following formula;

[0013] u k = sinθ k cosφ k

[0014] v k = sinθ k sinφ k

[0015] S2.2: Use the existing commonly used beam gain method to measure the orthogonality of the user channel matrix and calculate the user distance based on it; the beam gain minimization reflects the orthogonality between the matrix vectors as a whole and uses the greedy method to calculate the user group; calculate the signal-to-noise ratio and rate of the user group to maximize the rate; the beam gain uses the gain of the individual beam pointing to each user to the location of other users. The beam gain between users a and b is calculated using the following formula, where M v , M u Indicates the number of antenna elements in each row and column of the phased array antenna;

[0016]

[0017] where x u , x v is the relative position between users a and b, calculated using the following formula;

[0018] x u =u a -u b

[0019] x v =v a -v b

[0020] where u a , v a is the coordinate of user a calculated in cosine space using the S2.1 method, u b , v b is the coordinate of user b in the cosine space; j is the imaginary unit;

[0021] S2.3: Use the beam gain method to calculate the gain of 0 as the orthogonal position point of the user, and calculate the minimum distance between the orthogonal position of another user and this user as the distance measurement factor; the position of the user in the cosine space is (u k , v k ), the phased array element is M v ×M u When , the orthogonal position of the user in the cosine space can be expressed as p is from -M u Get M u All integers between -M v Get M v All integers between. The minimum distance s corresponding to users a and b a，b Use the following formula to calculate;

[0022]

[0023] where y u and v Indicates the horizontal and vertical spacing directions of the orthogonal positions closest to the user;

[0024]

[0025]

[0026] S2.4: Use the greedy method to select the user with the largest channel norm each time, and enumerate and select the remaining users so that the weighted sum of the beam gain and the minimum orthogonal distance of each group of users in the cosine space is minimized.

[0027] Assume that the set of users that have not been grouped is U. Each time a new group is divided, the greedy method is used to select the user a with the largest channel norm, that is, the user a that makes || h a ||max;h a is the user channel vector, which is 1×M v M u Vector, satisfying

[0028]

[0029] Each H k 1×M u A vector that satisfies

[0030]

[0031] in

[0032]

[0033] Suppose the set of users that the group already contains is V, enumerate and select the remaining users b, and for each user a in V, use the beam gain A calculated by S2.2 a,b and the minimum distance s calculated using S2.3 a,b , calculate the weighted sum S between users a and b a,b ;

[0034]

[0035] Among them, μ and γ are parameters that can be set;

[0036] Calculate the weighted sum for each user a in V, where the minimum value is Enumerate all remaining users b, calculate all weighted minimum values, and get the largest weighted minimum value The user b corresponding to this value is the next follow user. That is, the new user b satisfies

[0037]

[0038] π(b) is the minimum parameter corresponding to b; S2.5: If the minimum value π(b) of the focused user b is greater than the set threshold ψ, that is, there is no user satisfying the minimum value π(b) greater than the set threshold ψ, then the grouping ends and continues in the next group; otherwise, the user is assigned to this user group until all users have been allocated.

[0039] Furthermore, in S3, after calculating the user groups, a time division multiplexing method is used, and each group occupies a time period for multi-beam communication, thereby achieving the purpose of multi-user efficient communication.

[0040] A large-scale MIMO precoding grouping method for satellite communication of the present invention has the following advantages:

[0041] 1. The present invention utilizes a grouping method to enable the satellite to handle a large number of users;

[0042] 2. The improvement of the orthogonality of the user group channel of the present invention improves the signal-to-noise ratio of each user, thereby improving the rate and overall stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a packet flow chart of the massive MIMO satellite packet transmission system of the present invention;

[0044] Figure 2 Schematic diagram of a massive MIMO satellite packet transmission system of the present invention. DETAILED DESCRIPTION

[0045] In order to better understand the purpose, structure and function of the present invention, the following further describes in detail a large-scale MIMO precoding grouping method for satellite communication of the present invention in conjunction with the accompanying drawings.

[0046] The embodiment of the present invention discloses a method for grouping large-scale MIMO users by precoding, which mainly includes the following steps:

[0047] S1: Antenna configuration: A large-scale antenna array is used to obtain location information of large-scale users.

[0048] S2: Use beam gain method and orthogonal position method to group and maximize the orthogonality of user groups.

[0049] S3: Use time division multiplexing and multi-beam precoding methods to communicate with user groups.

[0050] Below Figure 2 Take the satellite massive MIMO transmission system shown as an example.

[0051] S1: Phased array has M v ×M u There are K antenna elements arranged in a matrix with a distance between the elements equal to half the transmission wavelength. There are K users who need to communicate. In a certain area, the elevation angle and azimuth angle between the users who need to communicate and the satellite are determined according to their positions, and the channel vector of the users is measured.

[0052] S2.1: For each user numbered k, 1≤k≤K, K is the number of users. Its pitch angle θ k , the azimuth is φ k , use the following formula to transfer to the coordinate point (u k , v k ), where u k , vk It represents the horizontal and vertical coordinates in this space and is calculated using the following formula;

[0053] u k = sinθ k cosφ k

[0054] v k = sinθ k sinφ k

[0055] S2.2: Use the existing commonly used beam gain method to measure the orthogonality of the user channel matrix and calculate the user distance based on it; the beam gain minimization reflects the orthogonality between the matrix vectors as a whole and uses the greedy method to calculate the user group; calculate the signal-to-noise ratio and rate of the user group to maximize the rate; the beam gain uses the gain of the individual beam pointing to each user to the location of other users. The beam gain between users a and b is calculated using the following formula, where M v , M u Indicates the number of antenna elements in each row and column of the phased array antenna;

[0056]

[0057] where x u , x v is the relative position between users a and b, calculated using the following formula;

[0058] x u =u a -u b

[0059] x v =v a -v b

[0060] where u a ,v a is the coordinate of user a calculated in cosine space using the S2.1 method, u b ,v b is the coordinate of user b in the cosine space; j is the imaginary unit;

[0061] S2.3: Use the place where the gain is 0 calculated by the beam gain method as the orthogonal position point of the user, and calculate the minimum distance between another user and the orthogonal position of this user as the distance measurement factor; the calculation shows that the orthogonal positions of the users are arranged in an array in the cosine space; the position of the user in the cosine space is (u k ,v k ), the phased array element is M v ×M uWhen , the orthogonal position of the user in the cosine space can be expressed as p is from -M u Get M u All integers between -M v Get M v All integers between. The minimum distance s corresponding to users a and b a,b Use the following formula to calculate;

[0062]

[0063] where y u and a Indicates the horizontal and vertical spacing directions of the orthogonal positions closest to the user;

[0064]

[0065]

[0066] S2.4: Use the greedy method to select the user with the largest channel norm each time, and enumerate and select the remaining users so that the weighted sum of the beam gain and the minimum orthogonal distance of each group of users in the cosine space is minimized.

[0067] Assume that the set of users that have not been grouped is U. Each time a new group is divided, the greedy method is used to select the user a with the largest channel norm, that is, the user a that makes || h a ||max;h a is the user channel vector, which is 1×M v M u Vector, satisfying

[0068]

[0069] Each H k 1×M u A vector that satisfies

[0070]

[0071] in

[0072]

[0073] Suppose the set of users that the group already contains is V, enumerate and select the remaining users b, and for each user a in V, use the beam gain A calculated by S2.2 a,b and the minimum distance s calculated using S2.3 a,b , calculate the weighted sum S between users a and b a,b ;

[0074]

[0075] Among them, μ and γ are parameters that can be set. According to simulation experiments, μ = 0.5 and γ = 2 are more appropriate.

[0076] Calculate the weighted sum for each user a in V, where the minimum value is Enumerate all remaining users b, calculate all weighted minimum values, and get the largest weighted minimum value The user b corresponding to this value is the next follow user. That is, the new user b satisfies

[0077]

[0078] π(b) is the minimum parameter corresponding to b; S2.5: If the minimum value π(b) of the focused user b is greater than the set threshold ψ, that is, there is no user satisfying the minimum value π(b) greater than the set threshold ψ, then the grouping ends and continues in the next group; otherwise, the user is assigned to this user group until all users have been allocated.

[0079] S3: The divided user groups can use the time division multiplexing communication method, that is, after calculating the user groups, the time division multiplexing method is used, and the precoding method including RZF is used to perform multi-beam communication for each group in each time period, so as to achieve the purpose of multi-user high-efficiency communication.

[0080] It is to be understood that the present invention is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the scope of protection of the present invention.

Claims

1. A large-scale MIMO precoding grouping method for satellite communication, characterized in that: The following steps are involved: S1: Establish a phased array model. The phased array has M v ×M u There are K antenna elements arranged in a matrix with a distance between the elements equal to half the transmission wavelength. There are K users who need to communicate. In an area, the elevation and azimuth angles of existing users with respect to the satellite are determined based on their positions, and the channel vectors of the users are measured. S2: The transmitter uses the user's channel vector and the principle of minimizing beam gain and the closest user orthogonal position to select users. In each iteration, a user index is selected to minimize the weighted sum of the channel vector norm, beam gain, and orthogonal position distance. The assigned user set is obtained to form a radio frequency link for sending transmission signals. S3: Communicate using time division multiplexing multi-beam communication method; The beam gain method used in S2 uses the signal-to-noise ratio of a single user's beam under a phased array under another user to measure the correlation between users. The method of nearest orthogonal position of users uses a discrete Fourier transform matrix to calculate the orthogonal position of users, and uses the distance of the user from the nearest orthogonal position to measure the correlation between users. The orthogonal position of users is minimized so that the beam directed to each user does not cover other users in the same group, reducing the interference between users after precoding; The S2 specifically includes the following steps: S2.1: For each user numbered k, its pitch angle θ k , the azimuth is φ k , use the following formula to transfer to the coordinate point (u k , v k ), where u k , v k It represents the horizontal and vertical coordinates in this space and is calculated using the following formula; u k =sinθ k cosφ k v k =sinθ k sinφ k S2.2: Use the beam gain method to measure the orthogonality of the user channel matrix and calculate the user distance based on it; the beam gain minimization reflects the orthogonality between the matrix vectors as a whole and uses the greedy method to calculate the user group; calculate the signal-to-noise ratio and rate of the user group to maximize the rate; The beam gain is the gain of the beam directed to each user to the location of other users. The beam gain between users a and b is calculated using the following formula, where M v , M u Indicates the number of antenna elements in each row and column of the phased array antenna; where x u , x v is the relative position between users a and b, calculated using the following formula; x u =u a -u b x v =v a -v b where u a , v a is the coordinate of user a calculated in cosine space using the S2.1 method, u b , v b is the coordinate of user b in the cosine space; j is the imaginary unit; S2.3: Use the place where the gain is 0 calculated by the beam gain method as the orthogonal position point of the user, and calculate the minimum distance between another user and the orthogonal position of this user as the distance measurement factor; the position of the user in the cosine space is (u k , v k ), the phased array element is M v ×M u When , the orthogonal position of the user in the cosine space is expressed as p is from -M u Get M u All integers between -M v Get M v All integers between; the minimum distance s corresponding to users a and b a，b Use the following formula to calculate; where y u and v Indicates the horizontal and vertical spacing directions of the orthogonal positions closest to the user; S2.4: Use the greedy method to select the user with the largest channel norm each time, and enumerate and select the remaining users so that the weighted sum of the beam gain and the minimum orthogonal distance of each group of users in the cosine space is minimized; Assume that the set of users that have not been grouped is U. Each time a new group is divided, the greedy method is used to select the user a with the largest channel norm, that is, the user a that makes || h a ||max;h a is the user channel vector, which is 1×M v M u Vector, satisfying Each H k 1×M u A vector that satisfies in Suppose the set of users that the group already contains is V, enumerate and select the remaining users b, and for each user a in V, use the beam gain A calculated by S2.2 a，b and the minimum distance s calculated using S2.3 a，b , calculate the weighted sum S between users a and b a，b ; Among them, μ and γ are the set parameters; Calculate the weighted sum for each user a in V, where the minimum value is Enumerate all remaining users b, calculate all weighted minimum values, and get the largest weighted minimum value The user b corresponding to this value is the next user to join the group; that is, the new user b satisfies π(b) is the minimum parameter corresponding to b; S2.5: If there is no user satisfying the minimum value π(b) greater than the set threshold ψ, the grouping ends and continues in the next group; otherwise, the user is assigned to this user group.

2. The satellite communication massive MIMO precoding grouping method according to claim 1, characterized in that: In S3, after the user groups are calculated, a time division multiplexing method is used, and each group occupies a time period for multi-beam communication, thereby achieving the purpose of multi-user efficient communication.

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