CN111901889B - A distributed uplink multi-user random access method - Google Patents

Abstract

The invention provides a distributed uplink multi-user random access method, which belongs to the field of communication. The method includes: a user with an access requirement randomly selects a pilot sequence from a set of pilot sequences according to an access strategy broadcast by the base station and sends it to the base station, and initiates an access request to the base station; The downlink pilot signal is normalized and broadcast to users in the cell as random access response information; the user who initiates the access request is based on the received random access response information combined with its own signal power and the broadcast strategy of the cell , to judge whether it can win among the users competing for the same pilot sequence, and the winning user resends the selected pilot sequence to the base station; the base station estimates the channel information according to the received secondary pilot information and demodulates the user identification code , and allocate dedicated pilot resources to users who have successfully demodulated. By adopting the present invention, efficient access of multiple users can be realized.

Description

A distributed uplink multi-user random access method

technical field

The present invention relates to the field of communications, in particular to a distributed uplink multi-user random access method.

Background technique

Random access is the first step for a user to establish an uplink communication connection with a base station. It has two main purposes: one is to establish an uplink synchronization relationship with the base station; the other is to request the base station to allocate uplink resources for data transmission.

The traditional contention-based random access scheme means that users send randomly selected pilot sequences to the base station. When multiple users select the same pilot sequence and a pilot collision occurs, the base station centrally solves the pilot collision problem. The goal is to minimize the pilot collision probability, thereby increasing the number of users who successfully access the network. However, in the face of the communication demands of a large number of users, the pilot collision problem is becoming more and more obvious. The centralized solution of pilot collision by the base station will inevitably bring a high collision rate to it, resulting in large user access delay and low efficiency. Therefore, the traditional centralized random access scheme for resolving pilot frequency conflicts has been unable to meet the needs of massive user access scenarios, and a novel and efficient random access scheme is urgently needed.

SUMMARY OF THE INVENTION

The embodiment of the present invention provides a distributed uplink multi-user random access method, which adopts a distributed pilot conflict resolution strategy to transfer the pilot conflict problem to the user end, and each user determines whether it wins the competition, not the base station. Specifying which user wins the competition by replying to the contention resolution message can significantly improve the access efficiency of multi-users in the cell, alleviate the performance loss caused by the centralized resolution of pilot conflicts by the base station, improve the probability of conflict resolution, and reduce user access delay. , so as to realize the efficient access of multiple users. The technical solution is as follows:

In one aspect, a distributed uplink multi-user random access method is provided, and the method is applied to electronic equipment, including:

A user with an access requirement randomly selects a pilot sequence from the pilot sequence set according to the access policy broadcast by the base station and sends it to the base station, and initiates an access request to the base station;

The base station obtains the normalized downlink pilot signal according to the received pilot signal, and broadcasts it to users in the cell as random access response information;

The user who initiates the access request judges whether it can win among the users competing for the same pilot sequence according to the random access response information received and combined with its own signal power and the broadcast strategy of the cell. The pilot sequence is resent to the base station;

The base station estimates the channel information to demodulate the user identification code according to the received secondary pilot information, and allocates dedicated pilot resources for the successfully demodulated users.

Further, the user with access needs randomly selects a pilot sequence from the pilot sequence set according to the access policy broadcast by the base station and sends it to the base station, and initiating an access request to the base station includes:

Using the prior knowledge of the broadcast channel, the base station broadcasts the access strategy to users in the cell according to the distribution characteristics of users in the cell;

中随机选取一个导频序列P_i发送至基站，向基站发起接入请求，其中，i＝1,2,...,λ_p，λ_p表示正交归一化可用导频序列的数目。According to the access policy broadcasted by the base station, users with access requirements can select from the pilot sequence set

A pilot sequence _{P i} is randomly selected from among the base stations and sent to the base station, where an access request is initiated to the base station, where i ₌ 1, 2, .

Further, the base station obtains the normalized downlink pilot signal according to the received pilot signal, and broadcasts the normalized downlink pilot signal as random access response information to users in the cell, including:

The base station obtains the sum y _i of the channel information of all users who select the same pilot sequence according to the received pilot signal;

The base station obtains a normalized downlink pilot signal by normalizing y _i , and uses it as random access response information;

The base station broadcasts the random access response information to users in the cell.

Further, the pilot signal received by the base station is expressed as:

表示P_i的转置；Z表示均值为0，方差为σ²的加性高斯白噪声；Among them, Y represents the pilot signal received by the base station, U _i represents the set of users who select the pilot sequence P _i , i=1, 2,...,λ _p , λ _p represents the pilot sequence available for orthogonal normalization The number of ; w _k is the transmit power of user k; h _k represents the channel between user k and the base station;

represents the transpose of _Pi ; Z represents additive white Gaussian noise with mean 0 and variance σ ² ;

The sum y _i of the channel information of all users who select the pilot sequence P _i is expressed as:

Among them, P _i ^* denotes the conjugate of P _i ; Z _i denotes additive white Gaussian noise with mean 0 and variance σ ² .

Further, the normalized downlink pilot signal is expressed as:

Wherein, W represents the normalized downlink pilot signal.

Further, according to the received random access response information and in combination with its own signal power and the broadcast strategy of the cell, the user who initiates the access request judges whether it can win among the users competing for the same pilot sequence, and the winner of the competition. The user resends the selected pilot sequence to the base station including:

与其选取的导频序列P_i进行相关运算，得到互相关运算的结果Q_k；The random access response information that user k will receive

Carry out a correlation operation with the selected pilot sequence P _i to obtain the result Q _k of the cross-correlation operation;

估计出选择相同导频序列P_i的所有用户的信号功率之和

Real part based on Q _k

Estimate the sum of the signal powers of all users who choose the same pilot sequence P _i

确定。User k adds a decision amount ξ(α _k ) on the basis of its own signal power, and then judges whether it wins the competition and re-conducts the frequency according to the strong user decision criterion. The strong user decision criterion is defined by w _k α _k λ _p +ξ(α _k )and

Sure.

表示为：Further, the random access response information received by user k

Expressed as:

表示h_k的共轭转置，

表示均值为0，方差为σ²的加性高斯白噪声；in,

represents the conjugate transpose of h _k ,

Represents additive white Gaussian noise with mean 0 and variance σ ² ;

The result of the cross-correlation operation Q _k is expressed as:

表示h_k的共轭转置，h_k表示用户k与基站之间的信道；λ_p表示正交归一化可用导频序列的数目；y_i表示选择导频序列P_i的所有用户的信道信息之和；Z_k表示均值为0，方差为σ²的加性高斯白噪声；Wherein, P _i ^* represents the conjugate of the pilot sequence P _i ;

Represents the conjugate transpose of h _k , h _k represents the channel between user k and the base station; λ _p represents the number of available pilot sequences for orthogonal normalization; y _i represents the channel of all users who select the pilot sequence P _i Sum of information; Z _k represents additive white Gaussian noise with mean 0 and variance σ ² ;

表示为：Estimate the sum of the signal powers of all users who choose the same pilot sequence P _i

Expressed as:

Among them, M represents the number of antennas on the base station side, w _k represents the transmit power of user k, α _k represents the large-scale fading coefficient, and max(·) represents the operation of taking the maximum value.

Further, the signal power of user k itself is w _k α _k λ _p .

Further, the strong user judgment criterion is expressed as:

则用户k竞争胜出，用户k将所选的导频序列P_i重新发送至基站；其中，T_k表示用户竞争胜出这一事件；if satisfied

Then the user k wins the competition, and the user k resends the selected pilot sequence P _i to the base station; wherein, T _k represents the event that the user wins the competition;

则用户k竞争失败，随机接入失败；其中，F_k表示用户竞争失败这一事件。if satisfied

Then the user k fails to compete and the random access fails; where F _k represents the event that the user fails to compete.

Further, the secondary pilot information includes: a user identification code and a pilot sequence that the user who wins the competition re-sends to the base station;

The base station estimates the channel information to demodulate the user identification code according to the received secondary pilot information, and allocates dedicated pilot resources for the successfully demodulated users, including:

After the base station receives the pilot sequence of the winning user again, it estimates the channel information of the user;

demodulate the subscriber identity code using the estimated channel information;

If the demodulation is successful, allocate a dedicated pilot resource for the user to complete subsequent data transmission;

If the demodulation fails, the user access fails.

In one aspect, an electronic device is provided, the electronic device includes a processor and a memory, the memory stores at least one instruction, and the at least one instruction is loaded and executed by the processor to implement the above-mentioned distributed uplink multiplexing. User random access method.

In one aspect, a computer-readable storage medium is provided, wherein at least one instruction is stored in the storage medium, and the at least one instruction is loaded and executed by a processor to implement the above distributed uplink multi-user random access method.

The beneficial effects brought by the technical solutions in the embodiments of the present invention include at least:

In the embodiment of the present invention, a user with an access requirement randomly selects a pilot sequence from the set of pilot sequences according to the access policy broadcast by the base station and sends it to the base station, and initiates an access request to the base station; the base station according to the received pilot signal The normalized downlink pilot signal is obtained and broadcast to users in the cell as random access response information. The base station does not care which users select the pilot sequence and whether the pilot sequence collides; According to the received random access response information and combined with its own signal power and the broadcast strategy of the cell, the requesting user judges whether it can win among the users competing for the same pilot sequence, and the winning user will use the selected pilot The sequence is retransmitted to the base station; the base station estimates the channel information according to the received secondary pilot information to demodulate the user identification code, and allocates dedicated pilot frequency resources for the users whose demodulation is successful. In this way, the distributed pilot conflict resolution strategy is adopted to transfer the pilot conflict problem to the user end, and each user determines whether it wins the competition, instead of the base station specifying which user wins the competition by replying to the contention resolution message. It can significantly improve the access efficiency of multi-users in the cell, alleviate the performance loss caused by the centralized resolution of pilot frequency conflicts by the base station, improve the probability of conflict resolution, and reduce the user access delay, thereby achieving efficient multi-user access.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings required in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention, which are very important to the art For those of ordinary skill, other drawings can also be obtained from these drawings without any creative effort.

1 is a schematic flowchart of a distributed uplink multi-user random access method provided by an embodiment of the present invention;

2 is a schematic structural diagram of a system model provided by an embodiment of the present invention;

FIG. 3 is a schematic structural diagram of an electronic device provided by an embodiment of the present invention.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

As shown in FIG. 1, an embodiment of the present invention provides a distributed uplink multi-user random access method. The method can be implemented by an electronic device, and the electronic device can be a terminal or a server. The method includes:

S101, a user with an access requirement randomly selects a pilot sequence from a pilot sequence set according to an access policy broadcast by the base station and sends it to the base station, and initiates an access request to the base station;

S102, the base station obtains a normalized downlink pilot signal according to the received pilot signal, and broadcasts it to users in the cell as random access response information;

S103, the user who initiated the access request judges whether it can win among the users competing for the same pilot sequence according to the received random access response information and in combination with its own signal power and the broadcast strategy of the cell, and the winning user will use the The selected pilot sequence is resent to the base station;

S104, the base station estimates the channel information according to the received secondary pilot information to demodulate the user identification code, and allocates dedicated pilot resources for the users whose demodulation is successful.

In the distributed uplink multi-user random access method provided by the embodiment of the present invention, a user with access needs randomly selects a pilot sequence from a set of pilot sequences according to an access policy broadcast by the base station, sends it to the base station, and initiates a call to the base station. Access request; the base station obtains the normalized downlink pilot signal according to the received pilot signal, and broadcasts it to the users in the cell as random access response information. The base station does not care which users select the pilot sequence, and Whether the pilot sequence collides; instead, the user who initiates the access request determines whether it can be among the users competing for the same pilot sequence according to the random access response information received and combined with its own signal power and the broadcast strategy of the cell. If the user wins the competition, the user who wins the competition resends the selected pilot sequence to the base station; the base station estimates the channel information according to the received secondary pilot information to demodulate the user identification code, and allocates dedicated pilot resources for the successfully demodulated users. In this way, the distributed pilot conflict resolution strategy is adopted to transfer the pilot conflict problem to the user end, and each user determines whether it wins the competition, instead of the base station specifying which user wins the competition by replying to the contention resolution message. It can significantly improve the access efficiency of multi-users in the cell, alleviate the performance loss caused by the centralized resolution of pilot conflicts by the base station, improve the probability of conflict resolution, and reduce the user access delay, thereby achieving efficient multi-user access.

In this embodiment, the distributed manner means that each user judges by himself whether he wins the competition, and the base station no longer specifies which user wins the competition by replying a contention resolution message.

In this embodiment, in order to simplify the system model, it is assumed that the base station is located in the center of the cell, the number of antennas on the base station side is M, there are K single-antenna user terminals (referred to as: users) in the cell, and there are λ _p orthonormal available pilot sequences for UL, and K >> λ _p . The channel between user k (1≤k≤K) and the base station is h _k =[h _1,k ,h _2,k ,...,h _m,k ,...,h _M,k ] ^T , where h _i,k is the channel transmission coefficient between user k and the i-th antenna at the base station, which can be determined by both large-scale fading and small-scale fading

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，通常与阴影衰落和路径损耗相关。当基站侧天线的数目M趋于无穷大时，用户k与基站之间的信道具有渐近最优传播特性，即：Among them, g _i,k indicates that the probability density function between user k and the i-th antenna at the base station is as follows:

The IID small-scale fading coefficient of , α _k represents the large-scale fading coefficient between user k and the base station, which is usually related to shadow fading and path loss. When the number M of antennas on the base station side tends to infinity, the channel between user k and the base station has an asymptotically optimal propagation characteristic, namely:

表示h_k的共轭转置。in,

represents the conjugate transpose of h _k .

In this embodiment, before S101, the base station broadcasts a reference signal, and each user estimates its large-scale fading coefficient α _k according to the reference signal, and completes synchronization with the base station.

In this embodiment, a user with an access requirement randomly selects a pilot sequence from a set of pilot sequences according to an access policy broadcast by the base station and sends it to the base station, and initiates an access request to the base station (S101) including:

A1, using the prior knowledge of the broadcast channel, the base station broadcasts the access strategy to the cell users according to the distribution characteristics of the cell users;

In this embodiment, using the prior knowledge of the broadcast channel, the base station broadcasts the access policy to the cell users in advance in the system message according to the distribution characteristics of the cell users, for example, the edge priority, fairness priority, efficiency priority and other criteria; wherein,

The edge priority criterion gives priority to edge user access, enhancing the success rate of edge user access;

The fairness priority criterion can balance the difference of channel gain strength among users, which is beneficial to realize the fairness of user competition;

The efficiency priority criterion can improve the efficiency of user access.

中随机选取一个导频序列P_i发送至基站，向基站发起接入请求，其中，i＝1,2,...,λ_p，λ_p表示正交归一化可用导频序列的数目。A2, users who have access requirements, according to the access policy broadcast by the base station, from the pilot sequence set

A pilot sequence _{P i} is randomly selected from among the base stations and sent to the base station, where an access request is initiated to the base station, where i ₌ 1, 2, .

In this embodiment, the traditional contention-based random access scheme is changed. Using the prior knowledge of the broadcast channel, the base station will broadcast the access policy to the user in advance. Then, the user initiates an access request according to the access policy broadcast by the base station, and the base station The access policy will also be adjusted in real time, so that multiple users in the cell can access efficiently.

In this embodiment, the base station obtains a normalized downlink pilot signal according to the received pilot signal, and broadcasts the normalized downlink pilot signal as random access response information to users in the cell (S102), including:

B1, the base station obtains the sum y _i of the channel information of all users who select the same pilot sequence according to the received pilot signal;

In this embodiment, the pilot signal Y received by the base station is expressed as:

Among them, U _i represents the set of users who select the pilot sequence P _i , i=1,2,...,λ _p ; w _k is the transmit power of user k; h _k represents the channel between user k and the base station; P _i ^T represents the transpose of _Pi ; Z represents additive white Gaussian noise with mean 0 and variance σ ² .

In this embodiment, y _i is expressed as:

Among them, P _i ^* denotes the conjugate of P _i ; Z _i denotes additive white Gaussian noise with mean 0 and variance σ ² .

In this embodiment, when the number of antennas M tends to infinity, it can be obtained:

Among them, γ _i is the sum of the signal powers of all users who select the same pilot, and σ ² is the noise variance;

B2, the base station obtains the normalized downlink pilot signal W by normalizing y _i , and uses it as random access response information;

In this embodiment, W is represented as:

表示P_i的转置。in,

represents the transpose of _Pi .

B3, the base station broadcasts the random access response information to the users in the cell.

In this embodiment, the user who initiates the access request judges whether it can win among users competing for the same pilot sequence according to the received random access response information and in combination with its own signal power and the broadcast strategy of the cell. The winning user resends the selected pilot sequence to the base station (S103) including:

与其选取的导频序列P_i进行相关运算，得到互相关运算的结果Q_k；C1, the random access response information that user k will receive

Carry out a correlation operation with the selected pilot sequence P _i to obtain the result Q _k of the cross-correlation operation;

表示为：In this embodiment,

Expressed as:

表示h_k的共轭转置，

表示均值为0，方差为σ²的加性高斯白噪声。in,

represents the conjugate transpose of h _k ,

Represents additive white Gaussian noise with mean 0 and variance σ ² .

In this embodiment, Q _k is expressed as:

表示h_k的共轭转置，Z_k表示均值为0，方差为σ²的加性高斯白噪声；in,

Represents the conjugate transpose of h _k , Z _k represents additive white Gaussian noise with mean 0 and variance σ ² ;

In this embodiment, when the number of antennas M tends to infinity, it can be obtained:

In this embodiment, since the imaginary part of Q _k only includes the noise part, the following approximate expression can be obtained by ignoring its imaginary part:

估计出选择相同导频序列P_i的所有用户信号功率之和

C2, based on the real part of Q _k

Estimate the sum of the signal power of all users choosing the same pilot sequence P _i

表示为：In this embodiment,

Expressed as:

Among them, max(·) represents the operation of taking the maximum value.

确定。C3, user k adds a judgment amount ξ(α _k ) on the basis of its own signal power, and then judges whether it wins the competition and re-conducts the frequency according to the strong user judgment criterion, where the strong user judgment criterion is determined by w _k α _k λ _p +ξ( α _k ) and

Sure.

In this embodiment, the signal power of user k itself is w _k α _k λ _p , where w _k is the transmit power of user k, α _k represents the large-scale fading coefficient, and λ _p represents the pilot sequence available for orthogonal normalization Number of.

In this embodiment, ξ(α _k ) is an offset related to α _k . In general, ξ(α _k )=0. When the base station broadcasts different access policies, the user will follow the broadcast policy of the base station. Make dynamic changes to ξ(α _k ).

In this embodiment, it is assumed that the access strategy broadcasted by the base station is the edge priority criterion. If the value of α _k of the edge user is small, the offset can take a positive value, that is, ξ(α _k )>0; If the value of _k is large, the offset can be zero, that is, ξ(α _k )=0. If the value of α _k of the non-edge user is large, the offset can take a negative value, that is, ξ(α _k )<0; if the value of α _k of the non-edge user is small, the offset can take zero, that is, ξ(α _k )=0. Under the edge priority criterion, when the non-edge user α _k is large enough, the access can be given up, and the access of the edge user is given priority.

In this embodiment, the strong user judgment criterion is expressed as:

则用户k竞争胜出，用户k将所选的导频序列P_i重新发送至基站，其中，T_k表示用户竞争胜出这一事件；if satisfied

Then the user k wins the competition, and the user k resends the selected pilot sequence P _i to the base station, where T _k represents the event that the user wins the competition;

则用户k竞争失败，该用户保持静止，随机接入失败，其中，F_k表示用户竞争失败这一事件。if satisfied

Then user k fails to compete, the user remains stationary, and random access fails, where F _k represents the event that user k fails to compete.

In this embodiment, the winning user also needs to send other information to the base station, for example, user identification code (ID information), so that the base station allocates dedicated pilot resources for the user in the next step.

In this embodiment, the base station estimates the channel information according to the received secondary pilot information to demodulate the user identification code, and allocates dedicated pilot resources for the successfully demodulated users (S104) including:

After the base station receives the pilot sequence of the winning user again, it estimates the channel information of the user;

demodulate the subscriber identity code using the estimated channel information;

If the demodulation is successful, a dedicated pilot frequency resource (specifically: a resource block corresponding to a certain pilot frequency) is allocated to the user, so as to complete the subsequent data transmission;

If the demodulation fails, the user access fails.

In this embodiment, the secondary pilot information includes: a user identification code and a pilot sequence that the winning user re-sends to the base station.

与导频序列P₀进行相关运算，进而估计出选择导频序列P₀的所有用户的信号功率之和，即公式(12)；边缘用户与非边缘用户的信号功率分别为：w_fα_fλ_p+ξ(α_f)与w_nα_nλ_p+ξ(α_n)，若

且

则表明非边缘用户UE_n竞争失败，边缘用户UE_f竞争胜出，UE_f可重复发送导频序列P₀，进而提高边缘用户的接入效率。In this embodiment, the system model shown in FIG. 2 is taken as an example to describe the distributed uplink multi-user random access method provided by the embodiment of the present invention. The base station (BS) is located in the center of the cell and is equipped with M antennas. The single-antenna users are evenly distributed in different positions of the cell. It is assumed that an edge user is UE _f and a non-edge user is UE _n , and their distances from the base station are d respectively. _f and d _n , according to the reference signal broadcast by the base station, the two users estimate the large-scale fading coefficients as α _f and α _n respectively, at this time α _f <α _n , each user in the cell will receive the access broadcast by the base station Strategies such as edge first, fairness first, or efficiency first. Assuming that the base station broadcasts the edge priority criterion in a certain period, the edge user UE _f knows that it is an edge user and finds that its large-scale fading coefficient α _{f is} small, so its offset takes a reasonable positive value; the non-edge user UE _n clearly If you are a non-edge user, if you find that its large-scale fading coefficient α _n is particularly large, then give up access directly, otherwise its offset takes a reasonable negative value, at this time ξ(α _f )>0>ξ(α _n ) . When they select the same pilot frequency P ₀ to send to the base station, the base station broadcasts random access response information (RAR), and the edge user UE _f and the non-edge user UE _n will receive the random access response information.

Carry out the correlation operation with the pilot sequence P ₀ , and then estimate the sum of the signal powers of all users who select the pilot sequence P ₀ , that is, formula (12); the signal powers of edge users and non-edge users are: w _f α _f λ _p +ξ(α _f ) and w _n α _n λ _p +ξ(α _n ), if

and

It means that the competition of the non-edge user UE _n fails, the edge user UE _f wins the competition, and the UE _f can repeatedly send the pilot sequence P ₀ , thereby improving the access efficiency of the edge user.

3 is a schematic structural diagram of an electronic device 600 according to an embodiment of the present invention. The electronic device 600 may vary greatly due to different configurations or performances, and may include one or more central processing units (CPU) 601 and One or more memories 602, wherein at least one instruction is stored in the memory 602, and the at least one instruction is loaded and executed by the processor 601 to implement the above distributed uplink multi-user random access method.

In an exemplary embodiment, a computer-readable storage medium, such as a memory including instructions, is also provided, and the instructions can be executed by a processor in a terminal to implement the above distributed uplink multi-user random access method. For example, the computer-readable storage medium may be a ROM, a random access memory (RAM), a CD-ROM, a magnetic tape, a floppy disk, an optical data storage device, or the like.

Those of ordinary skill in the art can understand that all or part of the steps in the above-mentioned embodiments can be implemented by hardware, and can also be implemented by hardware related to program instructions, and the program can be stored in a computer-readable storage medium. The storage medium mentioned may be a read-only memory, a magnetic disk or an optical disk, or the like.

The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection of the present invention. within the range.

Claims (3)

1. A distributed uplink multi-user random access method is characterized by comprising the following steps:

a user with access requirements randomly selects a pilot frequency sequence from the pilot frequency sequence set according to an access strategy broadcasted by the base station, sends the pilot frequency sequence to the base station and initiates an access request to the base station;

the base station obtains a normalized downlink pilot signal according to the received pilot signal, and broadcasts the normalized downlink pilot signal as random access response information to users in a cell;

the user initiating the access request judges whether the user can win the user competing for the same pilot frequency sequence according to the received random access response information and by combining the signal power of the user and the broadcasting strategy of the cell, and the user who wins the competition wins sends the selected pilot frequency sequence to the base station again;

the base station demodulates the user identification code according to the received secondary pilot frequency information estimation channel information and allocates exclusive pilot frequency resources for the successfully demodulated user;

the base station obtains a normalized downlink pilot signal according to the received pilot signal, and broadcasts the normalized downlink pilot signal as random access response information to users in a cell, wherein the step of broadcasting comprises the following steps:

the base station receivesThe pilot signal of (a) is obtained as the sum y of the channel information of all users selecting the same pilot sequence_i；

The base station passes y_iNormalizing to obtain a normalized downlink pilot signal, and using the normalized downlink pilot signal as random access response information;

the base station broadcasts the random access response information to users in the cell;

the pilot signal received by the base station is represented as:

where Y denotes a pilot signal received by the base station, U_iIndicating the selection of the pilot sequence P_iI 1,2_p，λ_pRepresenting the number of orthogonally normalized available pilot sequences; w is a_kThe transmit power for user k; h is_kRepresents the channel between user k and the base station;

represents P_iTransposing; z represents a mean of 0 and a variance of σ²Additive white gaussian noise of (1);

selecting a pilot sequence P_iIs received by all users, and the sum y of the channel information of all users_iExpressed as:

wherein,

represents P_iConjugation of (1); z_iRepresenting a mean of 0 and a variance of σ²Additive white gaussian noise of (1);

wherein, the normalized downlink pilot signal is expressed as:

wherein, W represents a normalized downlink pilot signal;

wherein, the user initiating the access request judges whether the user can win the user competing for the same pilot frequency sequence according to the received random access response information and combining the signal power of the user and the broadcast strategy of the cell, and the user competing for wining resends the selected pilot frequency sequence to the base station comprises:

random access response information to be received by user k

Pilot frequency sequence P selected by it_iPerforming correlation operation to obtain the result Q of the correlation operation_k；

Based on Q_kReal part of

Estimating the selection of the same pilot sequence P_iSum of signal powers of all users

User k adds a decision quantity xi (alpha) on the basis of own signal power_k) Then, according to the strong user decision criterion, judging whether the user wins the competition and retransmits the pilot frequency, wherein the strong user decision criterion is w_kα_kλ_p+ξ(α_k) And

is determined in which_kRepresenting a large scale fading coefficient;

wherein, the random access response information received by the user k

Expressed as:

wherein,

represents h_kThe conjugate transpose of (a) is performed,

representing a mean of 0 and a variance of σ²Additive white gaussian noise of (1);

result of cross-correlation operation Q_kExpressed as:

wherein,

represents the pilot sequence P_iConjugation of (1);

represents h_kConjugate transpose of (i), h_kRepresents the channel between user k and the base station; lambda [ alpha ]_pRepresenting the number of orthogonally normalized available pilot sequences; y is_iIndicating the selection of the pilot sequence P_iThe sum of the channel information of all users; z_kRepresenting a mean of 0 and a variance of σ²Additive white gaussian noise of (1);

estimating the selection of the same pilot sequence P_iSum of signal powers of all users

Expressed as:

wherein M represents the number of base station side antennas, w_kRepresenting the transmit power, alpha, of user k_kRepresents a large-scale fading coefficient, and max (-) represents a maximum value operation;

wherein, the signal power of the user k is w_kα_kλ_p；

Wherein the strong user decision criterion is expressed as:

if it satisfies

User k wins the contention and user k will select pilot sequence P_iRe-sending to the base station; wherein, T_kIndicating that the user competes for winning the event;

if it satisfies

The user k fails in competition and the random access fails; wherein, F_kIndicating an event that the user has failed the competition.

2. The method of claim 1, wherein the user with access requirement randomly selects a pilot sequence from a set of pilot sequences according to an access policy broadcasted by a base station, sends the pilot sequence to the base station, and initiates an access request to the base station comprises:

the base station broadcasts an access strategy to users in the cell according to the distribution characteristics of the users in the cell by using the prior knowledge of the broadcast channel;

users with access requirements are grouped from pilot sequences according to access policies broadcast by the base station

In the method, a pilot frequency sequence P is randomly selected_iSending the information to a base station, and initiating an access request to the base station, wherein i is 1,2_p，λ_pRepresenting the number of orthogonally normalized available pilot sequences.

3. The distributed uplink multi-user random access method according to claim 1, wherein the secondary pilot information includes: the user identification code and the competition winning user are retransmitted to the pilot frequency sequence of the base station;

the base station demodulates the user identification code according to the received secondary pilot frequency information estimation channel information, and allocates exclusive pilot frequency resources for the successfully demodulated user comprises the following steps:

after receiving the pilot frequency sequence of the competition winning user again, the base station estimates the channel information of the user;

demodulating the user identification code using the estimated channel information;

if the demodulation is successful, allocating dedicated pilot frequency resources for the user so as to complete subsequent data transmission;

if the demodulation fails, the user access fails.

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