CN115835408A - Distributed satellite uplink multi-user random access method and system - Google Patents

Abstract

The invention discloses a distributed satellite uplink multi-user random access method and system. A user can obtain a pilot sequence from an available pilot sequence set according to a preset probability threshold and send it to a base station. The base station generates a pilot sequence based on the pilot sequence. Precode the random access response information, and use the statistical estimation method to screen the users whose same pilot sequence satisfies the preset optimal channel gain according to the precoded random access response information, and obtain the user with the optimal channel gain. The base station accepts and demodulates the best The identification code of the user with excellent channel gain, and at the same time match the corresponding pilot sequence according to the identification code after demodulation; on the basis of the estimation model constructed by the statistical estimation method, the user can judge whether it has a pilot collision with other users, and then Reducing the probability of pilot collision is conducive to more user access, more practical and large-scale access scenarios, and provides a more accurate access method.

Description

Distributed satellite uplink multi-user random access method and system

technical field

The invention relates to the field of distributed satellite uplink multi-user random access technology, in particular to a distributed satellite uplink multi-user random access method and system.

Background technique

Traditional MIMO systems have two working modes, namely FDD and TDD.

In the FDD mode, paired spectrum is required to realize simultaneous uplink and downlink communication. Since the spectrum resources suitable for satellite communication are very tight, the cost of using paired spectrum resources to support user access is too high.

其中，g_i,k表示用户k与基站端第i根天线之间服从概率密度函数CN(0,1)的独立同分布的小尺度衰落系数，α_k表示用户k与基站之间的大尺度衰落系数，其通常与阴影衰落和路损相关；In a typical LEO satellite MIMO system model that only considers single-cell TDD, it is generally stipulated that the satellite base station is configured with M antennas, K ₀ single-antenna users are uniformly distributed in the cell, and there are N orthogonally normalized available guides in the cell. frequency sequence, and satisfy K ₀ ≥ N. Consider the channel information h _k =[h _1,k ,h _2,k ,....,h _M,k ] between user k and base station as:

Among them, g _i,k represents the independent and identically distributed small-scale fading coefficient between user k and the i-th antenna of the base station, which obeys the probability density function CN(0,1), and α _k represents the large-scale fading coefficient between user k and the base station fading coefficient, which is usually related to shadow fading and path loss;

h _k satisfies the following conditions:

Wherein, h _k ∈C ^M*1 is the channel gain vector of M antennas corresponding to the kth user.

The distributed satellite uplink multi-user random access scheme in the prior art can make full use of the characteristics of the massive MIMO system, but it lacks a user to judge whether it has a pilot collision with other users according to a certain criterion, and then adopts a certain strategy to reduce the A scheme with small pilot collision probability.

Contents of the invention

Aiming at the above-mentioned deficiencies in the prior art, the present invention provides a distributed satellite uplink multi-user random access method and system, which utilizes the estimation model constructed by the user using the statistical estimation method to determine whether the user has a pilot collision with other users , thereby reducing the pilot collision probability.

In order to achieve the above-mentioned purpose of the invention, the technical scheme adopted in the present invention is:

On the one hand, a distributed satellite uplink multi-user random access method includes the following steps:

S1. Obtain a pilot sequence from a set of available pilot sequences according to a preset probability threshold;

S2. Generate precoded random access response information according to the pilot sequence;

S3. Using the statistical estimation method, according to the precoded random access response information, the users with the same pilot sequence satisfying the preset optimal channel gain are screened, and the users with the optimal channel gain are obtained;

S4. Receive and demodulate the identification code of the user with the optimal channel gain, and at the same time match the corresponding pilot sequence according to the demodulated identification code.

Preferably, the pilot sequence in step S1 is expressed as:

Among them, Y _rec is the pilot sequence, ρ _k is the transmit power of the user, Z is the independent additive Gaussian noise, h _k is the channel gain vector of M antennas corresponding to the kth user, and W is the interference of adjacent cells , _Ai is the user set that selects the pilot _xi , and N is the total number of pilot sequences in the pilot sequence set.

Preferably, step S2 specifically includes the following steps:

A1. Using cross-correlation calculations, according to the pilot sequence, the sum of the user channel information corresponding to the pilot sequence is obtained;

A2. Optimize the sum of user channel information according to the channel characteristics of the MIMO system, and obtain the sum of optimized user channel information. The optimization process is expressed as:

Among them, y _r is the sum of user channel information, ∞ is the infinite symbol, ||.|| ² is the signal power, α _k is the channel gain, τ _p is the receiving gain, ω _t is the interference signal, and σ ² is the noise power;

A3. Calculate precoded random access response information according to the sum of optimized user channel information.

Preferably, the precoded random access response in step A3 is expressed as:

为预编码随机接入响应信息，Y_PRAR为预编码随机接入响应，q为下行传输功率，x_r为第r个导频序列，

为信道响应，

为小区间干扰，

为小区内干扰，

为优化后的用户信道信息之和。in,

is the precoded random access response information, Y _PRAR is the precoded random access response, q is the downlink transmission power, x _r is the rth pilot sequence,

for the channel response,

is inter-cell interference,

for intra-cell interference,

is the sum of optimized user channel information.

Preferably, step S3 specifically includes the following steps:

B1. Use the normalized pilot sequence to screen the precoded random access response information, and obtain the precoded random access response information after screening, expressed as:

为预编码随机接入响应信息，η_k ^H信道H上用户接收到的噪声，η_k为用户接收到的噪声，且满足：

为归一化的导频序列，

为接收到的信号共轭，y_r为实际接收到的信号；Among them, z _k is the filtered coded random access response information,

For precoding random access response information, η _k ^H is the noise received by the user on channel H, η _k is the noise received by the user, and satisfies:

is the normalized pilot sequence,

is the conjugate of the received signal, and y _r is the actual received signal;

B2. Optimizing the filtered precoding random access response information under preset conditions, and the optimized precoding random access response information is expressed as:

为基站端根据观测信号y_r对信道h_k的最小均方误差，e_k为估计误差，

为估计误差的共轭，G_k为第一参数，满足

V_k为第二参数，满足

Among them, z _k ^* is the optimized precoding random access response information,

is the minimum mean square error of the base station to the channel h _k according to the observed signal y _r , and e _k is the estimation error,

is the conjugate of the estimation error, G _k is the first parameter, and satisfies

V _k is the second parameter, satisfying

B3. Use the statistical estimation method to construct an estimation model, and filter the optimized precoded random access response information according to the estimation model, obtain the users who screen the same pilot sequence to meet the preset optimal channel gain, and use the screened users as the optimal channel gain Excellent channel gain users.

In the second aspect, a distributed satellite uplink multi-user random access system includes:

A pilot sequence acquisition module, configured to acquire a pilot sequence from a set of available pilot sequences according to a preset probability threshold;

A precoded random access response information generating module, configured to generate precoded random access response information according to the pilot sequence;

The optimal channel gain user acquisition module is used to use the statistical estimation method to screen the same pilot sequence to meet the preset optimal channel gain users according to the precoded random access response information, and obtain the optimal channel gain users;

The pilot sequence matching module is used to receive and demodulate the identification code of the user with the optimal channel gain, and match the corresponding pilot sequence according to the demodulated identification code.

The present invention has the following beneficial effects:

The user can obtain the pilot sequence from the available pilot sequence set according to the preset probability threshold and send it to the base station. The base station generates precoded random access response information based on the pilot sequence, and uses statistical estimation method to randomly The input response information screens out the users whose same pilot sequence satisfies the preset optimal channel gain, and obtains the users with the optimal channel gain. frequency sequence; on the basis of the estimation model constructed by the statistical estimation method, the user can judge whether it has a pilot collision with other users, thereby reducing the probability of pilot collision, which is conducive to more user access, more practical and large-scale access scenarios and provide more accurate access methods.

Description of drawings

Fig. 1 is a flow chart of the steps of a distributed satellite uplink multi-user random access method provided by the present invention;

Fig. 2 is the estimation result based on normalization error in the embodiment of the present invention;

Fig. 3 is the estimation result based on the mean square error of normalization in the embodiment of the present invention;

Fig. 4 is the relationship between the channel and the collision resolution probability in the embodiment of the present invention;

FIG. 5 is a comparison diagram of the average number of random access attempts in a crowded scene in an embodiment of the present invention;

FIG. 6 is a comparison diagram of success probabilities of random access in a crowded scene in an embodiment of the present invention.

Detailed ways

The specific embodiments of the present invention are described below so that those skilled in the art can understand the present invention, but it should be clear that the present invention is not limited to the scope of the specific embodiments. For those of ordinary skill in the art, as long as various changes Within the spirit and scope of the present invention defined and determined by the appended claims, these changes are obvious, and all inventions and creations using the concept of the present invention are included in the protection list.

On the one hand, as shown in FIG. 1 , an embodiment of the present invention provides a distributed satellite uplink multi-user random access method, including the following steps:

S1. Obtain a pilot sequence from a set of available pilot sequences according to a preset probability threshold;

Preferably, the pilot sequence in step S1 is expressed as:

Among them, Y _rec is the pilot sequence, ρ _k is the transmit power of the user, Z is the independent additive Gaussian noise, h _k is the channel gain vector of M antennas corresponding to the kth user, and W is the interference of adjacent cells , _Ai is the user set that selects the pilot _xi , and N is the total number of pilot sequences in the pilot sequence set.

In the embodiment of the present invention, ρ _k is the transmission power of the user, where ρ _k = 0 means that the user is not activated, Z is the independent additive Gaussian noise, which satisfies Z～CN(0,σ ² ), Z∈C ^{M *L} , h _k is the channel gain vector of M antennas corresponding to the kth user, satisfying: h _k ∈ C ^M*1 , W is the interference of adjacent cells, satisfying: W ∈ C ^M*L , _Ai is the selection Select the user set of pilot _xi , N is the total number of pilot sequences in the pilot sequence set, and for any leading sequence x _t has the following properties:

为第l个传输径下系数转置，*为标量形式下的共轭，ω_t为干扰信号，L为传播路径数，α_t,k为时刻t用户k的衰减值，

为t时刻干扰信号，用户k在时刻t的发射功率，β_w,l为相关因子。Where: |.| ² represents the power of the signal,

is the coefficient transposition under the lth transmission path, * is the conjugate in scalar form, ω _t is the interference signal, L is the number of propagation paths, α _t,k is the attenuation value of user k at time t,

is the interference signal at time t, the transmission power of user k at time t, and β _w,l is the correlation factor.

In the embodiment of the present invention, step S1 is specifically:

The user randomly obtains a pilot sequence from the set of available pilot sequences, and sends the selected pilot sequence to the base station, where the base station broadcasts a control signal, and each user can obtain its average channel gain α _k according to the control signal, so that Realize the signal synchronization between the user and the base station.

其中A_i表示选择导频x_i的用户集合，例如k＝1,k＝2∈A₁则说明用户1和2同时选择了导频序列x₁，其中该预设概率阈值可表示为：In the embodiment of the present invention, each user who has an access request to the base station randomly selects a pilot sequence from the pilot sequence set X={x ₁ ,x ₂ ,…,x _N } and sends it to the base station, using p ₀ Indicates the activation probability of the user, the probability that the user chooses the pilot sequence x _i is p ₀ /N, and the number of users |A _i | who choose this sequence obeys the binomial distribution with the parameter p ₀ /N, namely

Wherein A _i represents the set of users who select pilot _xi , for example, k=1, k=2∈A ₁ means that users 1 and 2 have selected pilot sequence x ₁ at the same time, where the preset probability threshold can be expressed as:

Among them, P _collision is the preset probability threshold, and K ₀ is the initial benchmark probability setting.

S2. Generate precoded random access response information according to the pilot sequence;

Preferably, step S2 specifically includes the following steps:

A1. Using cross-correlation calculations, according to the pilot sequence, the sum of the user channel information corresponding to the pilot sequence is obtained;

In the embodiment of the present invention, the base station performs a cross-correlation operation on the received pilot signal and any pilot sequence of the cell, and obtains the sum of channel information of all users who select the pilot sequence, expressed as:

为x_r的共轭形式，其中满足r＝1,2,...,N，x_r为第r个导频序列，L为传输径，||.||为求模计算符；Z′∈C^M*1为检测到的噪声，满足(0，1)分布，表示为：

其中，I_L表示为：单位矩阵。Among them, y _r is the sum of user channel information, Y _rec is the received signal matrix,

is the conjugate form of x _r , where r=1,2,...,N is satisfied, x _r is the rth pilot sequence, L is the transmission path, ||.|| is the modulo operator; Z' ∈C ^M*1 is the detected noise, which satisfies the (0, 1) distribution, expressed as:

Among them, _IL is expressed as: identity matrix.

A2. Optimize the sum of user channel information according to the channel characteristics of the MIMO system, and obtain the sum of optimized user channel information. The optimization process is expressed as:

Among them, y _r is the sum of user channel information, ∞ is the infinite symbol, ||.|| ² is the signal power, α _k is the channel gain, τ _p is the receiving gain, ω _t is the interference signal, and σ ² is the noise power;

In the embodiment of the present invention, further according to the channel characteristics of the MIMO system, when the number M of antennas tends to infinity, the above optimization process can be obtained.

A3. Calculate precoded random access response information according to the sum of optimized user channel information.

Preferably, the precoded random access response in step A3 is expressed as:

为预编码随机接入响应信息，Y_PRAR为预编码随机接入响应，q为下行传输功率，x_r为第r个导频序列，

为信道系数，

为小区间干扰，

为接收到的噪声，即：小区内干扰，

为优化后的用户信道信息之和。in,

is the precoded random access response information, Y _PRAR is the precoded random access response, q is the downlink transmission power, x _r is the rth pilot sequence,

is the channel coefficient,

is inter-cell interference,

is the received noise, namely: intra-cell interference,

is the sum of optimized user channel information.

满足：

用户接收到的噪声

满足：

从上式中可以看出，基站并不关心导频被哪些用户选择，以及导频是否发生碰撞，只是简单处理接收到的信息得到预编码随机接入响应信息，并广播给用户。In the embodiment of the present invention, the precoded random access response

satisfy:

Noise received by the user

satisfy:

It can be seen from the above formula that the base station does not care which users select the pilot and whether the pilot collides. It simply processes the received information to obtain precoded random access response information and broadcasts it to users.

S3. Screen the users whose same pilot sequence satisfies the preset optimal channel gain according to the precoded random access response information, and obtain the users with the optimal channel gain;

Preferably, step S3 specifically includes the following steps:

B1. Use the normalized pilot sequence to screen the precoded random access response information, and obtain the precoded random access response information after screening, expressed as:

为预编码随机接入响应信息，η_k ^H信道H上用户接收到的噪声，η_k为用户接收到的噪声，且满足：

为归一化的导频序列，

为接收到的信号共轭，y_r为实际接收到的信号；Wherein, z _k is the filtered coded random access response information, z _k is the screened coded random access response information,

For precoding random access response information, η _k ^H is the noise received by the user on channel H, η _k is the noise received by the user, and satisfies:

is the normalized pilot sequence,

is the conjugate of the received signal, and y _r is the actual received signal;

B2. Optimizing the filtered precoding random access response information under preset conditions, and the optimized precoding random access response information is expressed as:

为基站端根据观测信号y_r对信道h_k的最小均方误差，e_k为估计误差，

为估计误差的共轭，G_k为第一参数，满足

V_k为第二参数，满足

Among them, z _k ^* is the optimized precoding random access response information,

is the minimum mean square error of the base station to the channel h _k according to the observed signal y _r , and e _k is the estimation error,

is the conjugate of the estimation error, G _k is the first parameter, and satisfies

V _k is the second parameter, satisfying

以及筛选后的编码随机接入响应信息z_k，可得到：

并在噪声和小区干扰满足不随天线数M的增加而增加的条件下，则有：In the embodiment of the present invention, according to the channel vector properties

And the filtered coded random access response information z _k , can get:

And under the condition that the noise and cell interference do not increase with the increase of the number of antennas M, then:

同时令Re{z_k}表示接收信息，同时认为虚部均由噪声造成，则有：

由此估计选择同一个导频x_i的所有用户的功率之和为：

其中，max{·}表示取最大值操作，Re{·}表示取输入数据的实部；According to the above formula, the sum ε _i of the power of all users who choose the same pilot _xi can be defined, that is, the sum of the powers of all users who choose the same pilot _xi under cell interference is:

At the same time let Re{z _k } represent the received information, and consider that the imaginary part is caused by noise, then:

It is thus estimated that the sum of the powers of all users who choose the same pilot _xi is:

Among them, max{ } means to take the maximum value operation, and Re{ } means to get the real part of the input data;

Considering the uncorrelated Rayleigh fading channel, the channel between user k and base station: h _k CN(0,α _k I _M ), where M is the number of antennas, and α _k represents the large-scale fading between user k and base station Coefficients, which are usually related to shadow fading and path loss, I _M is the identity matrix;

Wherein, inter-adjacent cell interference is expressed as: v _k CN(0,Y _k I _L ), where L is the number of pilots, and inter-cell interference is independent of other signals;

则实际的信道矩阵可以表述为：

由于，

e_k表示估计误差，与信道估计

相互独立，

Assuming that the set A _i of users who select the sequence x _i is known at a certain moment, the minimum mean square error (MMSE) of the channel h _k estimated by the base station according to the observed signal y _r is:

Then the actual channel matrix can be expressed as:

because,

e _k represents the estimation error, which is related to the channel estimation

Independent,

则可得到优化后的预编码随机接入响应信息。It is not difficult to see from the MMSE estimation of h _k that

Then optimized precoding random access response information can be obtained.

B3. Use the statistical estimation method to construct an estimation model, and filter the optimized precoded random access response information according to the estimation model, obtain the users who screen the same pilot sequence to meet the preset optimal channel gain, and use the screened users as the optimal channel gain Excellent channel gain users.

Preferably, step B3 includes two inventive embodiments;

The first embodiment of the invention adopts a maximum likelihood (Maximum Likelihood, ML) estimation method, and its specific implementation process is:

则ε_i的ML估计式为：

通过对z_k的分析不难看出，

且

和

相互独立，则

于是ε_i的ML估计式可以被改写为：

其中，

等于G_k和

概率密度函数的卷积，

等于

的概率密度函数。First, the real and imaginary parts of z _k are separated, and z _k can be rewritten as

Then the ML estimation formula of ε _i is:

It is not difficult to see through the analysis of z _k that,

and

and

independent of each other, then

Then the ML estimator of ε _i can be rewritten as:

in,

is equal to G _k and

Convolution of the probability density function,

equal

The probability density function of .

δ₂＝σ²+Υ_k+ρ_kα_kL-δ₁，则

V_k～CN(0,δ₂)，于是有：make

δ ₂ ＝σ ² +Y _k +ρ _k α _k L-δ ₁ , then

V _k ～CN(0,δ ₂ ), then:

Among them, m=2M-1,

The following equations exist for all non-negative integer m and real numbers A and B:

Among them, γ( ) is the lower incomplete gamma function,

Using the above information you can get:

in,

是

的概率密度函数，且

于是because

yes

The probability density function of , and

then

将

和

代入ε_i的ML估计式即可得到

Will

and

Substituting into the ML estimation formula of ε _i can get

The second embodiment of the invention uses approximate estimation to estimate ε _i , and its specific steps are:

的均值可以得到ε_i的一个封闭形式的近似估计：according to

The mean of ε _i can be approximated in a closed form by:

According to the above formula inversion:

Therefore, it is estimated that the sum of the powers of all users who select the same pilot _xi (priori knowledge: must be greater than the power of user k) is:

After that, according to the calculated ε _i,k , the user judges whether he is a strong user (the user with the highest power among users who choose the same pilot frequency), that is, whether the power of user k satisfies: ρ _k α _k L＞ε _{i ,k} -ρ _k α _k L, namely: ρ _k α _k L＞ε _i,k /2;

In order to maximize the average number of resolved conflicts or minimize the risk of false positives (or negatives), a bias coefficient θ _k is introduced, which can be obtained as:

R _k : ρ _k α _k L＞ε _i,k /2+θ _k , user k is a strong user

J _k :ρ _k α _k L<ε _i,k /2+θ _k , user k is a weak user

In the two embodiments of the invention, each user decides whether to retransmit the same pilot according to the judgment result (strong users retransmit, weak users do not). In addition, the user also needs to send other information to the base station, such as a user identification code, so that the base station can allocate a dedicated data pilot sequence to the user in the next step.

S4. Demodulate the identification code of the user with the optimal channel gain, and match the corresponding pilot sequence according to the identification code.

In the embodiment of the present invention, after receiving the pilot sequence of the user again, the base station first estimates the channel information of the user, and then uses the estimated channel information to demodulate the message sent by the user. If the demodulation is successful, a dedicated data pilot sequence is temporarily assigned to the user, and subsequent data transmission is completed. Otherwise, the user fails to access.

In the second aspect, the embodiment of the present invention provides a distributed satellite uplink multi-user random access system, including:

A pilot sequence acquisition module, configured to acquire a pilot sequence from a set of available pilot sequences according to a preset probability threshold;

A precoded random access response information generating module, configured to generate precoded random access response information according to the pilot sequence;

The optimal channel gain user acquisition module is used to use the statistical estimation method to screen the same pilot sequence to meet the preset optimal channel gain users according to the precoded random access response information, and obtain the optimal channel gain users;

The pilot sequence matching module is used to receive and demodulate the identification code of the user with the optimal channel gain, and match the corresponding pilot sequence according to the demodulated identification code.

A distributed satellite uplink multi-user random access system provided by an embodiment of the present invention includes all the beneficial effects of the above-mentioned distributed satellite uplink multi-user random access method.

Carry out multiple groups of experiments in the embodiment of the present invention:

1) Estimation error

图2为归一化的均方误差(Normalization Mean Squared Errors，NMSEs)，即

The performance of the signal gain ε _i obtained by the three estimation methods and the influence of the number of antennas on its performance are compared. The simulation results are shown in Figure 2 and Figure 3; where the value of ε _i is 20, all users and base stations in the cell use full power to send information, that is, ρ _k =q=1, and set the number of pilots N=30. Figure 1 shows the normalized error, namely

Figure 2 shows the normalized mean squared errors (Normalization Mean Squared Errors, NMSEs), namely

优于

时，ML估计具有最小的NMSEs，但ML估计需要复杂的计算量，因此

是更为合适的选择。It can be seen from Figure 2 and Figure 3 that the performance of these three estimators is poor when M<25, but they are asymptotically unbiased as M increases, and when M>50, the NMSEs are less than 10 ^-1 . From the point of view of positive deviation, all the estimated values tend to overestimate the estimated value. It can be seen from the figure that when

superior to

When , ML estimation has the smallest NMSEs, but ML estimation requires complex computation, so

is a more appropriate choice.

2) Relationship between channel and collision resolution probability

Considering that the channel has a certain impact on whether the pilot collision can be successfully resolved, the embodiment of the present invention is based on the LEO satellite with a height of 1175km and a minimum elevation angle of the user terminal of 29.5° for simulation, wherein the cell radius is set to 1000km, and the active users in the cell The number is 5000, the number of available pilots is 10, and each user accesses the network with a probability of 0.5%. Figure 4 and Figure 5 show the relationship between the probability of successful pilot collision resolution and the number of base station antennas under different channels; it can be seen that the distributed random access protocol depends on the strengthening and good propagation characteristics of the MIMO channel. When M=1, the probability of collision resolution is 20-50%, but when M=20, it increases significantly to 75-90%. For M > 20, the probability of collision resolution continues to increase, but at a slower rate. Uncorrelated Rayleigh fading works best; the LoS model performs slightly worse because the variance of path losses is lower, which makes it harder to assign a single strongest user; the NTN channel model is somewhere in between.

(3) The average number of random access attempts in crowded scenarios

其中图5显示了作为K₀的函数，每个用户进行随机接入尝试的平均次数。It has been mentioned above that the distributed random access protocol can solve the pilot conflict problem in large-scale random access, but the main purpose of the random access protocol is to enable each user to successfully access after as few access attempts as possible. . In the embodiment of the present invention, the simulation parameters are set as M=64, N=10 and K ₀ ∈[0,10000]. Each user accesses the network with a probability of 0.1%, and if it does not successfully access, the user will decide whether to send the pilot access again with a probability of 0.5. If the user does not successfully access after sending 10 pilots (including the initial one), the transmission is stopped, indicating that the access failed. Considering uncorrelated Rayleigh fading, the simulation is carried out with and without cell interference, and the error term is set as

Figure 5 shows the average number of random access attempts per user as a function of K ₀ .

(4) The success probability of random access in crowded scenarios

Figure 6 shows the probability of successful access between the traditional random access scheme and the distributed random access scheme, which can be understood as the success rate of a user's access. It can be seen that the distributed random access scheme is compared with The success rate of the traditional solution can be increased by about 20%, can support more user access, and is more suitable for large-scale access scenarios.

The performance analysis result of the embodiment of the present invention is represented by the following formula:

Based on the analysis results of the incoherent Rayleigh fading channel, the probability of the user retransmitting the pilot can be obtained as:

in,

It can be seen that in the distributed satellite uplink multi-user random access method and system provided by the embodiments of the present invention, on the basis of the estimation model constructed by the statistical estimation method, the user can judge whether there is a pilot collision with other users, thereby reducing The small pilot collision probability is conducive to more user access, more practical and large-scale access scenarios, and provides a more accurate access method.

The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It should be understood that each procedure and/or block in the flowchart and/or block diagram, and a combination of procedures and/or blocks in the flowchart and/or block diagram can be realized by computer program instructions. These computer program instructions may be provided to a general purpose computer, special purpose computer, embedded processor, or processor of other programmable data processing equipment to produce a machine such that the instructions executed by the processor of the computer or other programmable data processing equipment produce a An apparatus for realizing the functions specified in one or more procedures of the flowchart and/or one or more blocks of the block diagram.

These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing apparatus to operate in a specific manner, such that the instructions stored in the computer-readable memory produce an article of manufacture comprising instruction means, the instructions The device realizes the function specified in one or more procedures of the flowchart and/or one or more blocks of the block diagram.

These computer program instructions can also be loaded onto a computer or other programmable data processing device, causing a series of operational steps to be performed on the computer or other programmable device to produce a computer-implemented process, thereby The instructions provide steps for implementing the functions specified in the flow chart or blocks of the flowchart and/or the block or blocks of the block diagrams.

In the present invention, specific examples have been applied to explain the principles and implementation methods of the present invention, and the descriptions of the above examples are only used to help understand the method of the present invention and its core idea; meanwhile, for those of ordinary skill in the art, according to this The idea of the invention will have changes in the specific implementation and scope of application. To sum up, the contents of this specification should not be construed as limiting the present invention.

Those skilled in the art will appreciate that the embodiments described here are to help readers understand the principles of the present invention, and it should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical revelations disclosed in the present invention without departing from the essence of the present invention, and these modifications and combinations are still within the protection scope of the present invention.

Claims (6)

1. A distributed satellite uplink multi-user random access method is characterized in that, comprising the following steps: S1. Obtain a pilot sequence from a set of available pilot sequences according to a preset probability threshold; S2. Generate precoded random access response information according to the pilot sequence; S3. Using the statistical estimation method, according to the precoded random access response information, the users with the same pilot sequence satisfying the preset optimal channel gain are screened, and the users with the optimal channel gain are obtained; S4. Receive and demodulate the identification code of the user with the optimal channel gain, and at the same time match the corresponding pilot sequence according to the demodulated identification code. 2. according to the distributed satellite uplink multi-user random access method in claim 1, it is characterized in that, in the step S1, the pilot sequence is represented as:

Among them, Y _rec is the pilot sequence, ρ _k is the transmit power of the user, Z is the independent additive Gaussian noise, h _k is the channel gain vector of M antennas corresponding to the kth user, and W is the interference of adjacent cells , A _i is the user set that selects the pilot _xi , and N is the total number of pilot sequences in the pilot sequence set. 3. according to the distributed satellite uplink multi-user random access method in claim 2, it is characterized in that, step S2 specifically comprises the following steps: A1. Using cross-correlation calculations, according to the pilot sequence, the sum of the user channel information corresponding to the pilot sequence is obtained; A2. Optimize the sum of user channel information according to the channel characteristics of the MIMO system, and obtain the sum of optimized user channel information. The optimization process is expressed as:

Among them, y _r is the sum of user channel information, ∞ is the infinite symbol, ||.|| ² is the signal power, α _k is the channel gain, τ _p is the receiving gain, ω _t is the interference signal, and σ ² is the noise power; A3. Calculate precoded random access response information according to the sum of optimized user channel information. 4. according to the distributed satellite uplink multi-user random access method described in claim 3, it is characterized in that, in the step A3, the precoded random access response is expressed as:

in,

is the precoded random access response information, Y _PRAR is the precoded random access response, q is the downlink transmission power, x _r is the rth pilot sequence,

for the channel response,

is inter-cell interference,

for intra-cell interference,

is the sum of optimized user channel information. 5. according to the distributed satellite uplink multi-user random access method described in claim 4, it is characterized in that, step S3 specifically comprises the following steps: B1. Use the normalized pilot sequence to screen the precoded random access response information, and obtain the precoded random access response information after screening, expressed as:

Among them, z _k is the filtered coded random access response information,

For precoding random access response information, η _k ^H is the noise received by the user on channel H, η _k is the noise received by the user, and satisfies:

CN(0,σ ² ),

is the normalized pilot sequence,

is the conjugate of the received signal, and y _r is the actual received signal; B2. Optimizing the filtered precoding random access response information under preset conditions, and the optimized precoding random access response information is expressed as:

Among them, z _k ^* is the optimized precoding random access response information,

is the minimum mean square error of the base station to the channel h _k according to the observed signal y _r , and e _k is the estimation error,

is the conjugate of the estimation error, G _k is the first parameter, and satisfies

V _k is the second parameter, satisfying:

B3. Use the statistical estimation method to construct an estimation model, and filter the optimized precoded random access response information according to the estimation model, obtain the users who screen the same pilot sequence to meet the preset optimal channel gain, and use the screened users as the optimal channel gain Excellent channel gain users. 6. A distributed satellite uplink multi-user random access system, characterized in that it comprises: A pilot sequence acquisition module, configured to acquire a pilot sequence from a set of available pilot sequences according to a preset probability threshold; A precoded random access response information generating module, configured to generate precoded random access response information according to the pilot sequence; The optimal channel gain user acquisition module is used to use the statistical estimation method to screen the same pilot sequence to meet the preset optimal channel gain users according to the precoded random access response information, and obtain the optimal channel gain users; The pilot sequence matching module is used to receive and demodulate the identification code of the user with the optimal channel gain, and match the corresponding pilot sequence according to the demodulated identification code.

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