Multi-User Selection Method and System Based on Orthogonal Reference Frame

Abstract

The present invention discloses a multi-user selection method and system based on an orthogonal reference frame. The method of the present invention includes the following steps: S1, constructing an orthogonal reference frame according to the base station antenna dimension; S2, for each user, defining a corresponding index set according to the channel information; S3, selecting users according to the obtained index set. According to the constructed orthogonal reference frame and channel estimation information, the present invention selects a set of user combinations with less multi-user interference, thereby reducing the computational complexity and improving the system throughput, and thus further improving the performance of the communication system.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless communication, and particularly relates to a multi-user method and system based on an orthogonal reference frame. Background Art

[0002] A multi-user MIMO system allows a base station to communicate with multiple users simultaneously. Compared with a single-user MIMO, the system performance can be further improved. However, the limited number of antennas at the base station restricts the number of transmit beams that can be formed, thus limiting the number of users that can simultaneously access the wireless communication system. In densely populated areas, a large number of wireless devices are waiting to connect to the wireless communication network. Therefore, user scheduling with user selection as the core is crucial for the normal operation of a large-scale MIMO system.

[0003] The spectral efficiency of large-scale MIMO is closely related to the signal-to-interference-plus-noise ratio (SINR) of each user. Users that strongly interfere with each other should not transmit simultaneously in the same time slot, so as to obtain the maximum system SINR. However, the complexity of selecting the user combination with the highest SINR is extremely high, and it is necessary to exhaustively search all possible user combinations. When the number of users waiting to access the communication system is large, this is obviously impractical.

[0004] In view of the above technical problems, the present invention proposes a technical solution for multi-user selection based on an orthogonal reference frame. Summary of the Invention

[0005] In view of the above technical problems, the present invention provides a multi-user method and system based on an orthogonal reference frame, which reduces the computational complexity and improves the spectral efficiency of the system.

[0006] To achieve the above object, the present invention adopts the following technical methods:

[0007] The multi-user selection method based on an orthogonal reference frame includes the steps of:

[0008] S1. Construct an orthogonal reference frame according to the base station antenna dimension;

[0009] S2. For each user, define a corresponding index set according to its channel information;

[0010] S3. Select users according to the index set obtained above.

[0011] As a preferred solution, in step S2, the definition method is as follows: approximate the channel information vector with a linear combination of several vectors in the reference frame, and define the index set of its vectors as the index set.

[0012] As a preferred solution, in step S3, the selection method is as follows: Arrange the users in ascending order according to the number of elements in the index set, ensure that the channel modulus length of the selected users is greater than a fixed value, and make the index sets of the selected users pairwise disjoint until the number of selected users reaches the capacity of the communication system.

[0013] As a preferred solution, in step S1, the orthogonal reference frame is:

[0014]

[0015] where j represents the imaginary unit, M is the number of base station antennas, and {α 1 , α 2 , …, α M} are M points uniformly selected on [-π, π], and the column vectors generated therefrom are represented as follows:

[0016]

[0017] where the superscript T represents the transpose of the vector.

[0018] As a preferred solution, step S2 specifically includes the steps:

[0019] S2.1 Obtain the correlation matrix according to the user channel and the orthogonal reference frame;

[0020] S2.2 Preliminarily screen the users according to the correlation matrix and retain their index sets.

[0021] As a preferred solution, in step S2.1, the correlation matrix obtained from the user channel information and the orthogonal reference frame is:

[0022] D = [d 1 d 2 … d K T

[0023] where K is the number of users to communicate, and d k is a vector measuring the correlation magnitude between the channel h k of the k-th user and the column vectors in the orthogonal reference frame B, and is represented as follows:

[0024]

[0025] where H represents the conjugate transpose of the matrix, |·| represents taking the absolute value, and ||·|| 2 represents the Frobenius norm.

[0026] In step S2.2, the elements in d k are arranged in descending order, and l elements are selected and added successively to obtain: ​

[0027] λ k = d k,1 +…+ d k,l , l ∈ {1, 2, …, Q}

[0028] Where l is a value not greater than Q. If λ k satisfies the following conditions:

[0029] λ k ≥ λ

[0030] Where λ is a fixed value. If the above conditions are met, retain the index set Ω composed of the user and the subscript of its corresponding orthogonal reference frame k , otherwise, if l = Q and it is still less than the predetermined threshold, exclude the user and its corresponding index set.

[0031] As a preferred solution, step S3 specifically includes the steps:

[0032] S3.1 Obtain the user index set Ω according to the above steps k , record Ω k The number of elements in it is denoted as n k ;

[0033] S3.2 In the first iteration, select the users with the number of elements in the index set Ω k being 1, and determine whether they meet the user retention conditions;

[0034] S3.3 In the second iteration, select the users with the number of elements in the index set Ω k being 2, and determine whether they meet the user retention conditions;

[0035] S3.4 In the third iteration, select the users with the number of elements in the index set Ω k being 3, and determine whether they meet the user retention conditions;

[0036] S3.5 Iterate according to the above steps until the communication system capacity is reached.

[0037] As a preferred solution, in step S3.1, according to the user index set Ω obtained according to the above steps k , record that the number of elements in Ω k is n k .

[0038] In step S3.2, in the first iteration, screen out the set of users that meet the retention conditions, that is, the set of users with the number of elements in the index set being 1 is:

[0039]

[0040] Where There are t user metrics with the number of elements in the index set being 1, and their order is arranged from largest to smallest according to the channel modulus length, and the channel modulus lengths of their users are all greater than the fixed value ψ, and satisfy the following conditions: 1 That is, there are no identical elements in the index sets of any two users in ζ. And determine whether the number of selected users has reached the capacity N of the communication system

[0041]

[0042] That is, ζ 1 There are no identical elements in the index sets of any two users. And determine whether the number of selected users has reached the capacity N of the communication system K That is, if not, put the elements in ζ 1 into the set storing the selected users That is, And continue the next iteration. Otherwise, select the first N 1 users in ζ K as the users accessing the communication system and terminate the loop.

[0043] In step S3.3, in the second iteration, filter out the set of users that meet the retention conditions, that is, the set of users with the number of elements in the index set being 2 is:

[0044]

[0045] Among them, There are t user metrics with the number of elements in the index set being 2, and their order is arranged from largest to smallest according to the channel modulus length, and the channel modulus lengths of their users are all greater than the fixed value ψ, and satisfy the following conditions: 2 That is, there are no identical elements in the index sets of any two users in ζ, and the index sets of the users in ζ

[0046]

[0047]

[0048] That is, ζ 2 There are no identical elements in the index sets of any two users, and the index sets of the users in ζ 1 and the users in ζ 2 also have no identical elements. Put ζ 2 into to get:

[0049]

[0050] Judge whether the number of elements in it has reached the capacity N of the communication system K If not, continue the next iteration. Otherwise, select the first N users in K as the users accessing the communication system and terminate the loop.

[0051] In step S3.4, at the 3rd iteration, the user set that meets the retention condition is filtered out. That is, the user set with 3 elements in the index set is:

[0052]

[0053] Among them, are t 3 user metrics with 3 elements in the index set. Their order is arranged from largest to smallest according to the channel modulus length, and the channel modulus lengths of their users are all greater than the fixed value ψ and meet the following conditions:

[0054]

[0055]

[0056] That is, ζ 3 has no identical elements in the index sets of any two users, and ζ 1 , ζ 2 and ζ 3 also have no identical elements in the index sets of their users. Put ζ 3 into to get:

[0057]

[0058] Judge whether the number of elements in has reached the capacity N K of the communication system. If not, continue the next iteration. Otherwise, select the first N users in K as the users accessing the communication system and terminate the loop.

[0059] In step S3.5, iterate continuously according to the above steps until the capacity of the communication system is reached, and then stop the loop.

[0060] The present invention provides a multi-user selection scheme system based on an orthogonal reference framework, including an orthogonal reference framework construction module, a preliminary selection module, a modulus length comparison module, and an index set comparison module connected in sequence;

[0061] The orthogonal reference framework construction module constructs an orthogonal reference framework according to the base station antenna dimension;

[0062] The preliminary selection module preliminarily determines the retained users and the index set of the corresponding orthogonal reference framework with the help of the orthogonal reference framework according to the estimated value of the channel information.

[0063] The modulus length comparison module is used to judge the user selection priority when the number of users with the same subscript is more than 1.

[0064] An index set comparison module, which is used to filter the optimal user set by comparing the selected user and the to-be-selected user index sets.

[0065] The beneficial effects of the present invention are as follows:

[0066] The method and system for selecting users using an orthogonal reference frame according to the present invention select a set of user combinations with less multi-user interference based on the constructed orthogonal reference frame and channel estimation information, thereby reducing the computational complexity and improving the system throughput, and thus further improving the performance of the communication system. Description of the Drawings

[0067] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0068] Figure 1 is the flowchart of the multi-user selection method based on the orthogonal reference frame according to the present invention;

[0069] Figure 2 is the comparison diagram between the multi-user selection method based on the orthogonal reference frame and the random user selection according to the present invention;

[0070] Figure 3 is the structural schematic diagram of the multi-user selection system based on the orthogonal reference frame according to the present invention. Detailed Embodiments

[0071] The following illustrates the embodiments of the present invention through specific specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0072] Embodiment 1:

[0073] As Figure 1 shown, in this embodiment, a specific specific example is used to illustrate the method of the present invention. The present invention proposes a multi-user selection method based on an orthogonal reference frame.

[0074] The specific application case is as follows:

[0075] Taking 100 users, one base station with 128 antennas as an example. Table 1 below gives the general parameter settings, and a multi-user selection scheme is carried out according to the parameters in Table 1.

[0076] Table 1 Parameter Settings

[0077] parameter setting <![CDATA[Base Station Antenna N t > 128 <![CDATA[The number of receiving antennas N per user r > 1 number of users to communicate with, K 100 <![CDATA[Communication system capacity N K > 20 orthogonal reference frame, N 128 signal-to-noise ratio, ρ 6,8,10,12,14,16 number of clusters, P 6

[0078] A multi-user selection method based on an orthogonal reference framework in this embodiment specifically includes the following steps:

[0079] S1. Construct an orthogonal reference framework according to the base station antenna dimension;

[0080] S2. For each user, define a corresponding index set according to its channel information;

[0081] S3. Select users according to the index set obtained above.

[0082] Specifically, in step S2, the definition method is as follows: approximate the channel information vector with a linear combination of several vectors in the reference framework, and define the index set of its vectors as the index set.

[0083] Specifically, in step S3, the selection method is as follows: arrange the users in ascending order according to the number of elements in the index set, ensure that the channel modulus length of the selected users is greater than a fixed value, and make the index sets of the selected users pairwise disjoint until the number of selected users reaches the capacity of the communication system.

[0084] The method for selecting users using an orthogonal reference framework in the present invention selects a set of user combinations with less multi-user interference according to the constructed orthogonal reference framework and channel estimation information, thereby reducing the computational complexity and improving the system throughput, so the performance of the communication system is further improved.

[0085] Specifically, in this embodiment:

[0086] Suppose the large-scale antenna system includes 100 single-antenna users, one base station, and the base station is equipped with 128 antennas and the base station adopts a uniform linear array (ULA) arrangement. The channel information from the base station to user k is expressed as:

[0087] h k =Ac

[0088] where w is Gaussian noise with zero mean and variance σ 2 and A is the channel steering vector matrix, which is expressed as follows:

[0089]

[0090] where θ 1 ,θ 2, …, θ 6 is the azimuth angle of arrival of the corresponding path, and c is the complex gain coefficient vector of the channel. The elements therein are the complex gain coefficients of the corresponding paths and are expressed as follows:

[0091] c = [c 1 c 2 … c 6 T

[0092] Specifically, step S1 is to construct an orthogonal reference frame B according to the base station antenna dimension, which is expressed as follows:

[0093]

[0094] where j represents the imaginary unit, 128 is the number of base station antennas, and {α 1 , α 2 , …, α 128} are 128 points uniformly selected on [-π, π]. The column vectors generated therefrom are expressed as follows:

[0095]

[0096] where the superscript T represents the transpose of the vector.

[0097] Step S2 includes the steps of:

[0098] S2.1 Obtain the correlation matrix according to the user channel and the orthogonal reference frame;

[0099] S2.2 Preliminarily screen users according to the correlation matrix and retain their index sets.

[0100] In this embodiment, in step S2.1, the correlation matrix obtained from the user channel information and the orthogonal reference frame is:

[0101] D = [d 1 d 2 … d 100 T

[0102] where 100 is the number of users to communicate, and d k is a vector measuring the correlation between the channel h of the k-th user k and the column vectors in the orthogonal reference frame B, which is expressed as follows:

[0103]

[0104] where H represents the conjugate transpose of the matrix, |·| represents taking the absolute value, and ||·|| 2 represents the Frobenius norm.

[0105] ​​In step S2.2, arrange the elements in d k in descending order, and select l elements to add them up successively to obtain:

[0106] λ k = d k,1 +…+ d k,l , l ∈ {1, 2, …, 5}

[0107] where l is a value not greater than 5. If λ k satisfies the following condition:

[0108] λ k ≥ 0.63

[0109] where 0.63 is a fixed value. If the above conditions are met, retain the index set Ω k composed of the user and the corresponding subscript of the orthogonal reference frame. Conversely, if it is still less than the predetermined threshold when l = 5, exclude the user and its corresponding index set.

[0110] In step S3, the following steps are included:

[0111] S3.1 Obtain the user index set Ω k according to the above steps, and record the number of elements in Ω k as n k ;

[0112] S3.2 In the first iteration, select the users with the number of elements in the index set Ω k being 1, and determine whether they meet the user retention conditions;

[0113] S3.3 In the second iteration, select the users with the number of elements in the index set Ω k being 2, and determine whether they meet the user retention conditions;

[0114] S3.4 In the third iteration, select the users with the number of elements in the index set Ω k being 3, and determine whether they meet the user retention conditions;

[0115] S3.5 Continuously iterate according to the above steps until the communication system capacity is reached.

[0116] In this embodiment, according to the user index set Ω k obtained by the above steps, record that the number of elements in Ω k is n k .

[0117] In step S3.2, in the first iteration, screen out the set of users that meet the retention conditions, that is, the set of users with the number of elements in the index set being 1 is:

[0118]

[0119] Among them, are t user metrics with the number of elements in the index set being 1, and their order is arranged from largest to smallest according to the channel modulus length, and the channel modulus lengths of their users are all greater than the fixed value 20, and satisfy the following conditions: 1 1

[0120]

[0121] That is, ζ 1 There are no identical elements in the index sets of any two users in. And judge whether the number of selected users has reached the capacity 20 of the communication system, that is, if not, put the elements in ζ 1 into the set for storing the selected user collection , that is And continue the next iteration. Otherwise, select the first 20 users in ζ 1 as the users accessing the communication system and terminate the loop.

[0122] In step S3.3, in the second iteration, filter out the user set that meets the retention conditions, that is, the user set with the number of elements in the index set being 2 is:

[0123]

[0124] Among them, are t user metrics with the number of elements in the index set being 2, and their order is arranged from largest to smallest according to the channel modulus length, and the channel modulus lengths of their users are all greater than the fixed value 20, and satisfy the following conditions: 2

[0125]

[0126]

[0127] That is, ζ 2 There are no identical elements in the index sets of any two users in, and the users in ζ 1 and the index sets of the users in ζ 2 also have no identical elements. Put ζ 2 into to get:

[0128]

[0129] Judge whether the number of elements in has reached the capacity 20 of the communication system. If not, continue the next iteration. Otherwise, select the first 20 users in as the users accessing the communication system and terminate the loop.

[0130] In step S3.4, at the 3rd iteration, the user set that meets the retention condition is filtered out. That is, the user set with 3 elements in the index set is:

[0131]

[0132] Among them, are t 3 user metrics with 3 elements in the index set. Their order is arranged from largest to smallest according to the channel modulus length, and the channel modulus lengths of their users are all greater than the fixed value 20 and meet the following conditions:

[0133]

[0134]

[0135] That is, there are no identical elements in the index sets of any two users in ζ 3 , and there are also no identical elements in the index sets of the users in ζ 1 , ζ 2 and ζ 3 . Put ζ 3 into to get:

[0136]

[0137] Judge whether the number of elements in has reached the capacity 20 of the communication system. If not, continue the next iteration. Otherwise, select the first 20 users in as the users accessing the communication system and terminate the loop.

[0138] In step S3.5, iterate continuously according to the above steps until the communication system capacity is reached and the loop is stopped.

[0139] The user channels of the users accessing the communication system are obtained from the user set as and perform ZF precoding on it to obtain the precoding matrix, which is expressed as:

[0140]

[0141] From this,

[0142]

[0143] Among them, x K = [x 1 , x 2 , …, x 14 T is the pilot information sent by the base station. Then the throughput of the l k th user is expressed as follows:​

[0144]

[0145] Thus, the throughput of the multi-user communication system can be obtained as follows:

[0146]

[0147] Referring to Figure 2 As shown, when the signal-to-noise ratio is 10 dB, the system throughput of randomly selecting 20 users is about 161.6 bits pcu. Under the condition of the same signal-to-noise ratio, the simulation shows that the throughput of the multi-user selection method of the present invention is about 168.1 bits pcu, and as the system signal-to-noise ratio increases, the system throughput also increases.

[0148] Embodiment 2:

[0149] Referring to Figure 3 As shown, this embodiment provides a multi-user selection system based on an orthogonal reference frame, which is based on the selection method described in Embodiment 1 above, and includes an orthogonal reference frame construction module, a preliminary selection module, a modulus comparison module, and an index set comparison module connected in sequence;

[0150] The orthogonal reference frame construction module constructs an orthogonal reference frame according to the base station antenna dimension;

[0151] The preliminary selection module preliminarily determines the reserved users and the index set of the corresponding orthogonal reference frame with the help of the orthogonal reference frame according to the estimated value of the channel information.

[0152] The modulus comparison module is used to judge the user selection priority when the number of users with the same subscript is more than 1.

[0153] The index set comparison module is used to screen the best user set by comparing the index sets of the selected users and the to-be-selected users.

[0154] It should be noted that for the multi-user selection system based on the orthogonal reference frame provided in this embodiment, other contents can refer to Embodiment 1 and will not be elaborated here.

Claims

1. Multi - user selection method based on orthogonal reference frame, characterized in that it includes the following steps: S1. Construct an orthogonal reference frame according to the base station antenna dimension; S2. For each user, define a corresponding index set according to its channel information; S3. Select users according to the index set obtained above; In step S1, the orthogonal reference frame is as follows: where \(j\) represents the imaginary unit, \(M\) is the number of base station antennas, and \(\{\alpha\) 1 ,\alpha\) 2 ,\cdots,\alpha\) M}\) are \(M\) points uniformly selected on \([-\pi,\pi]\), and the column vector generated therefrom is represented as follows: where the superscript T represents the transpose of the vector; In step S2, the definition method is as follows: approximate the channel information vector with a linear combination of several vectors in the reference frame, and define the index set of its vectors as the index set; Step S2 specifically includes the following steps: S2.

1. Obtain the correlation matrix according to the user channel and the orthogonal reference frame; S2.

2. Preliminarily screen users according to the correlation matrix and retain the index set; In step S3, the selection method is as follows: arrange users in ascending order according to the number of elements in the index set, ensure that the channel modulus of the selected users is greater than a fixed value, and make the index sets of the selected users pairwise disjoint until the number of selected users reaches the capacity of the communication system; Step S3 specifically includes the following steps: S3.1, according to the obtained user index set Ω k , record Ω k The number of elements in it is denoted as n k ; S3.

2. At the first iteration, select users with one element in the index set Ω and determine whether they meet the user retention criteria; k ​ S3.

3. At the second iteration, select users with two elements in the index set Ω k and determine whether they meet the user retention criteria; S3.

4. At the 3rd iteration, select users with 3 elements in the index set Ω k and determine whether they meet the user retention criteria; S3.

5. Iterate according to the above steps until the capacity of the communication system is reached.

2. The multi - user selection method based on orthogonal reference frame according to claim 1, characterized in that in step S2.1, the correlation matrix obtained from the user channel information and the orthogonal reference frame is: D = [d 1 d 2 …d K T ​ where K is the number of users to communicate, and d k is a vector measuring the correlation magnitude between the channel h of the k-th user k and the column vectors in the orthogonal reference frame B, and is expressed as follows: where H represents the conjugate transpose of a matrix, |·| represents taking the absolute value, and ||·|| 2 represents the Frobenius norm; In step S2.2, the elements in d k are arranged in descending order, and l elements are selected and added successively to obtain: λ k = d k,1 + … + d k,l , l ∈ {1, 2, …, Q} where l is a value not greater than Q; if λ k satisfies the following conditions: λ k ≥ λ Where λ is a fixed value; if the above conditions are satisfied, the index set Ω composed of the user and the corresponding subscript of the orthogonal reference frame is retained. k On the contrary, if it is still less than the predetermined threshold when l = Q, the user and its corresponding index set are excluded.

3. The multi - user selection method based on orthogonal reference frame according to claim 1, characterized in that In step S3.1, according to the obtained user index set Ω k , record to obtain Ω k , and the number of elements in it is n k ; in step S3.2, in the first iteration, screen out the user set that meets the retention conditions, that is, the user set with the number of elements in the index set being 1 is: Among them, are t user metrics with the number of elements in the index set being 1, and the order is arranged from largest to smallest according to the channel modulus length, and the user channel modulus lengths are all greater than the fixed value ψ, and satisfy the following conditions: 1 ​ That is, ζ 1 There are no identical elements in the index sets of any two users; and determine whether the number of selected users has reached the capacity N of the communication system K , that is, if not, then put the elements in ζ 1 into the set storing the selected users , that is and continue the next iteration. Otherwise, select the first N 1 users in ζ K as the users accessing the communication system and terminate the loop; in step S3.3, in the second iteration, screen out the user set that meets the retention conditions, that is, the user set with the number of elements in the index set being 2 is: Among them, are t user metrics with the number of elements in the index set being 2, and the order is arranged from largest to smallest according to the channel modulus length, and the user channel modulus lengths are all greater than the fixed value ψ, and satisfy the following conditions: 2 ​ That is, ζ 2 There are no identical elements in the index sets of any two users in, and ζ 1 The users in and ζ 2 There are also no identical elements in the index sets of the users in; Put ζ 2 into to get: Determine whether the number of elements in has reached the capacity N of the communication system K , if not, continue with the next iteration, otherwise, select the first N K users in as the users accessing the communication system and terminate the loop; in step S3.4, in the third iteration, screen out the user set that meets the retention conditions, that is, the user set with the number of elements in the index set being 3 is: Among them, are t user metrics with the number of elements in the index set being 3, and the order is arranged from largest to smallest according to the channel modulus length, and the user channel modulus lengths are all greater than the fixed value ψ, and satisfy the following conditions: 3 ​ That is, ζ 3 There are no identical elements in the index sets of any two users in, and ζ 1 , ζ 2 and ζ 3 also have no identical elements in the index sets of the users in; Put ζ 3 into to get: Judge whether the number of elements in has reached the capacity N of the communication system K , if not, continue with the next iteration, otherwise, select the first N K users in as the users accessing the communication system and terminate the loop; in step S3.5, continuously iterate according to the above steps until the capacity of the communication system is reached, and stop the loop.

4. Multi - user selection system based on orthogonal reference frame, characterized in that it includes an orthogonal reference frame construction module, a preliminary selection module, a modulus comparison module, and an index set comparison module connected in sequence; The orthogonal reference frame construction module constructs an orthogonal reference frame according to the base station antenna dimension; The preliminary selection module preliminarily determines the retained users and the index set of the corresponding orthogonal reference frame according to the estimated channel information with the help of the orthogonal reference frame; The modulus comparison module is used to judge the user selection priority when the number of users with the same subscript is more than 1; The index set comparison module is used to screen the best user set by comparing the index sets of the selected users and the to - be - selected users; In the orthogonal reference frame construction module, the orthogonal reference frame is as follows: where \(j\) represents the imaginary unit, \(M\) is the number of base station antennas, \(\{\alpha 1 ,\alpha 2 ,\ldots,\alpha M \}\) are \(M\) points uniformly selected on \([-\pi,\pi]\), and the column vector generated therefrom is represented as follows: where the superscript T represents the transpose of the vector; In the preliminary selection module, the definition method is as follows: approximate the channel information vector with a linear combination of several vectors in the reference frame, and define the index set of its vectors as the index set; The preliminary selection module is specifically as follows: Obtain the correlation matrix according to the user channel and the orthogonal reference frame; According to the correlation matrix, initially screen users and retain the index set; In the modulus comparison module, the selection method is as follows: Arrange users in ascending order according to the number of elements in the index set, ensure that the channel modulus of the selected users is greater than a fixed value, and make the index sets of the selected users pairwise disjoint until the number of selected users reaches the capacity of the communication system; The modulus comparison module is specifically as follows: According to the obtained index set Ω of the user k , record Ω k The number of elements in it is denoted as n k ; At the first iteration, select the user with the number of elements in the index set Ω equal to 1, and determine whether it meets the user retention condition; k ​ At the second iteration, select the user whose number of elements in the index set Ω k is 2, and determine whether it meets the user retention condition; At the 3rd iteration, select users in the index set Ω k with 3 elements, and determine whether they meet the user retention conditions; Iterate according to the above steps until the capacity of the communication system is reached.

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