WO2021136472A1 - Two user uplink transmission rateless encoding method and rateless code decoding method - Google Patents

Abstract

A two user uplink transmission rateless encoding degree distribution optimization method, a two user uplink transmission rateless encoding and decoding method, a two user uplink transmission method, and a two user uplink transmission rateless encoding and decoding apparatus. Said optimization method comprises: according to extrinsic information transfer analysis of a decoding process of two users and channel state statistical information, determining an optimization problem of optimizing a degree distribution coefficient for two user rateless encoding using minimal signal-to-noise ratio as a target and when Raptor encoding is performed according to a preset average code length; solving the optimization problem, and determining an optimal degree distribution for two user rateless encoding.

Description

Rateless coding method and rateless code decoding method for two-user uplink transmission

Related application

This application claims the priority of the Chinese patent application filed on December 31, 2019, the application number is 201911419716.4, and the invention title is "Rateless Encoding Method and Rateless Code Decoding Method for Two-User Uplink Transmission", the entire content of which is approved The reference is incorporated in this application.

Technical field

This application relates to the field of communication technology, in particular to a method for optimizing the frequency distribution of rateless coding for two-user uplink transmission, a rateless coding method for two-user uplink transmission, a rateless code decoding method for two-user uplink transmission, and two-user uplink transmission. An uplink transmission method, a rateless coding device for two-user uplink transmission, and a rateless code decoding device for two-user uplink transmission.

Background technique

Distributed Antenna Systems (DAS) is a system that can provide wireless coverage for a certain area, and can effectively solve the problem of indoor wireless communication coverage blind spots. The antennas in the distributed multi-antenna system are scattered in different geographical locations of the cell, which can effectively improve the coverage at the edge of the cell. In addition, since the spatial access distance from the user terminal to each remote radio head (RRH) antenna of the distributed multi-antenna system is reduced, the system transmission power can be effectively reduced and the system performance can be improved. However, compared with the traditional cellular network, the network status and channel status of the distributed multi-antenna system are more complicated and variable. Noise, interference and channel fading have a great impact on the quality and transmission reliability of electromagnetic wave signals. Severe noise, interference and channel fading may even cause the interruption of the communication process. In order to counter the unstable factors of the wireless channel and ensure the reliable transmission of information, error control technology is often used to protect the message to be sent in the actual transmission process. Among them, channel coding is an effective error control technology.

Traditional fixed-rate channel coding needs to obtain user channel information and use Hybrid Automatic Repeat reQuest (HARQ for short) when decoding fails, which will increase the overhead of the digital forward link. However, if the rateless code is used for channel coding, only the receiver needs to feed back an Acknowledge Character (ACK) signal to indicate successful decoding, which can effectively reduce signaling overhead.

The research of rateless codes mainly includes degree distribution design, decoding method design, etc. The degree distribution function is directly related to the performance of rateless codes, which determines the success rate of decoding, decoding overhead and decoding complexity, etc. Design for rateless codes The key to the code is to construct an appropriate degree distribution function. The traditional degree distribution function optimization method is aimed at Additive White Gaussian Noise (AWGN) channels, and requires the network central node to know the global network channel state information for optimization, which will bring greater system signaling overhead , Reduce system transmission efficiency.

Summary of the invention

According to various embodiments of the present application, a method for optimizing the frequency distribution of rateless coding for uplink transmission of two users is provided, which is applied to a distributed multi-antenna system under a block fading channel, and the method includes:

According to the statistical information of the channel state and the external information transfer analysis of the decoding process of the two users, it is determined that when the Raptor coding is performed according to the preset average code length, with the goal of minimizing the signal-to-noise ratio, the degree distribution of the two users' rateless coding is optimized Optimization problem of coefficients;

Solve the optimization problem, and determine the optimized degree distribution of the rateless coding of the two users.

In some of the embodiments, the preset average code length is determined according to the statistical information of the channel state of the block fading channel.

In some of the embodiments, the optimization problem is listed as follows:

The constraints of the optimization problem include:

(1) The degree distribution of the edge of the output node of the LT code graph and the constraint condition C1:

(2) Decoding start condition C2 at the receiving end:

ω _i,1 >ε,i=1,2

(3) Decoding convergence condition C3 at the receiving end:

For all H _q , i=1, 2

(4) The constraint condition C4 of preset average code length:

Among them, P _th is the transmit power threshold;

Is a constant irrelevant to the channel matrix; {ω _i,d } is the degree distribution coefficient of the edge of the output node of the LT code graph of user i;

Is the variance of independent Gaussian white noise; d _c is the maximum degree of the edge of the output node of the LT code graph; ω _i,d is the degree distribution coefficient of the edge of the output node of the degree d in the LT code graph corresponding to user i; ε; Is a preset value greater than zero;

In order for the output node of the LT code graph corresponding to user i to return the external information of the input node of the LT code graph under the maximum number of iterations l′;

Is the external information threshold; H _q is the channel matrix in the q-th case where the distribution space of the channel matrix H is discretized into Q cases, q=1,...,Q; K is the length of the original information; R _p is no rate The code rate of the LDPC code in the encoding; Pr(H _q ) is the probability that the channel matrix is H _q ; C(H _q , P _th ) is the channel matrix H _q and the theoretical reach of user i when the transmission power is P _th Rate; L is the preset average code length of the Raptor code.

In some of the embodiments, solving the optimization problem and determining the optimized degree distribution of the rateless coding of the two users includes:

Using a differential evolution algorithm to determine the optimal solution of the optimization problem;

According to the degree distribution coefficient of the edge of the output node of the LT code graph corresponding to the optimal solution, the degree distribution of the LT code graph without the rate code corresponding to the two users is calculated.

According to various embodiments of the present application, a rateless coding method for two-user uplink transmission is also provided, which is applied to two sending node devices for uplink transmission of user information to a distributed multi-antenna system under a block fading channel. include:

Determining the optimized degree distribution of the two users' rate-free coding according to the method for optimizing the degree distribution of the rate-free coding;

According to the degree distribution of the rateless coding, rateless coding is performed on the user information of the two users respectively.

According to various embodiments of the present application, there is also provided a two-user uplink transmission method, which is applied to a distributed multi-antenna system under a block fading channel, and the method includes:

The distributed multi-antenna system receives uplink transmission signals from multiple remote radio heads to obtain the uplink transmission signals of the two users; wherein, the uplink transmission signal is based on the rateless coding method described in the second aspect. The user information of the two users is obtained by rate-free coding and then modulation;

The distributed multi-antenna system performs preprocessing and quantization processing on the uplink transmission signals of the two users respectively to obtain the quantized signals of the two users;

The distributed multi-antenna system performs soft demodulation on the quantized signal of the other of the two users according to the decoding output of one of the two users in the previous round of decoding, and then uses The belief propagation algorithm performs joint decoding to obtain the user information of the two users respectively.

In some of the embodiments, the initial decoding output of the one user is used to soft demodulate the quantized signal of the other user in the first round of decoding, wherein the initial decoding output is 1.

According to various embodiments of the present application, a rateless code decoding method for uplink transmission of two users is also provided, which is applied to a distributed multi-antenna system under a block fading channel. The uplink transmission of the two users adopts the method described in the third aspect. In the two-user uplink transmission method, the rate-free code decoding method for the two-user uplink transmission includes:

For each of the two users, iterative decoding is performed on the entire decoding graph until the average value of the log-likelihood ratio of the input node of each of the two users exceeds a preset threshold;

For each of the two users, iterative decoding is performed on the LDPC code pattern respectively until the decoding is correct or the maximum number of iterations is reached.

According to various embodiments of the present application, there is also provided a rateless encoding device for two-user uplink transmission, which is applied to a sending node device, and the device includes:

A determining module, configured to determine the optimized degree distribution of the two users for the rateless coding according to the method for optimizing the degree distribution of the rateless coding according to the first aspect;

The rateless coding module is configured to perform rateless coding on the user information of the sending node device according to the degree distribution of the rateless coding.

According to various embodiments of the present application, a rateless code decoding device for uplink transmission of two users is also provided, which is applied to a distributed multi-antenna system under a block fading channel. The uplink transmission of the two users adopts the method described in the third aspect. In the two-user uplink transmission method, the rateless code decoding device for the two-user uplink transmission includes:

The first decoding module is configured to perform iterative decoding on the entire decoding graph for each of the two users until the average value of the log likelihood ratio of the input node of each of the two users Exceed the preset threshold;

The second decoding module is configured to respectively perform iterative decoding on the LDPC code pattern for each of the two users until the decoding is correct or the maximum number of iterations is reached.

According to various embodiments of the present application, a distributed multi-antenna system is also provided. The distributed multi-antenna system is applied to a block fading channel. The distributed multi-antenna system includes multiple remote radio heads and baseband processing. Unit pool, where

The remote radio head is used to receive an uplink transmission signal and send the uplink transmission signal to the baseband processing unit pool after preprocessing and quantization processing; wherein the uplink transmission signal is according to the second aspect The rateless coding method is obtained by performing rateless coding on the user information of the two users and then modulating;

The baseband processing unit pool is used to perform soft demodulation on the quantized signal of the other user of the two users according to the decoding output of one user of the two users in the previous round of decoding process, and then The belief propagation algorithm is used for joint decoding to obtain the user information of the two users respectively.

In some of these embodiments, the baseband processing unit pool is also used to perform soft demodulation on the quantized signal of the other user with the initial decoding output of the one user in the first round of decoding, where all The initial decoding output is 1.

In some of the embodiments, the baseband processing unit pool includes a first decoding module and a second decoding module, wherein,

The first decoding module is configured to perform iterative decoding on the entire decoding graph for each of the two users until the log-likelihood ratio of the input node of each of the two users is determined The average value exceeds the preset threshold;

The second decoding module is configured to respectively perform iterative decoding on the LDPC code pattern for each of the two users until the decoding is correct or the maximum number of iterations is reached.

The above-mentioned two-user uplink transmission optimization method for the frequency distribution of the rateless coding, the rateless coding method for the two-user uplink transmission, the rateless code decoding method for the two-user uplink transmission, the two-user uplink transmission method, and the no-rate for the two-user uplink transmission The encoding device and the rateless code decoding device for two-user uplink transmission have the following advantages:

In the distributed multi-antenna system under the block fading channel, according to the statistical information of the channel state and the external information transfer analysis of the decoding process of the two users, it is determined that the Raptor encoding is performed according to the preset average code length to minimize the signal noise The goal is to optimize the optimization problem of the degree distribution coefficients of the two-user rateless coding; solve the optimization problem, determine the optimal method of the degree distribution of the two-user rateless coding, and solve the problem of the rateless coding in the related technology. The degree optimization needs to know the global network channel state information, which causes the problem of high system signaling overhead, which reduces the signaling overhead of rateless coding.

Description of the drawings

In order to better describe and illustrate the embodiments and/or examples of those applications disclosed herein, one or more drawings may be referred to. The additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed applications, the currently described embodiments and/or examples, and the best mode of these applications currently understood.

Fig. 1 is a schematic diagram of an uplink transmission process of a two-user distributed multi-antenna system according to an embodiment of the present application.

FIG. 2 is a flowchart of a method for optimizing the frequency distribution of rateless coding for uplink transmission of two users according to an embodiment of the present application.

Fig. 3 is a preferred flowchart of a method for optimizing the frequency distribution of rateless coding for uplink transmission of two users according to an embodiment of the present application.

Fig. 4 is a flowchart of a rateless coding method for two-user uplink transmission according to an embodiment of the present application.

Fig. 5 is a flowchart of a two-user uplink transmission method according to an embodiment of the present application.

Fig. 6 is a flowchart of a process of joint decompression and decoding of the received signals of two users by the distributed multi-antenna system according to an embodiment of the present application.

Fig. 7 is a flowchart of a rateless code decoding method for two-user uplink transmission according to an embodiment of the present application.

FIG. 8 is a schematic diagram of joint decoding of a pool of baseband processing units according to an embodiment of the present application.

Fig. 9 is a structural block diagram of a rateless coding apparatus for two-user uplink transmission according to an embodiment of the present application.

Fig. 10 is a structural block diagram of a rateless code decoding device for two-user uplink transmission according to an embodiment of the present application.

FIG. 11 is a schematic structural diagram of a distributed multi-antenna system according to an embodiment of the present application.

FIG. 12 is a schematic diagram of a preferred structure of a distributed multi-antenna system according to an embodiment of the present application.

Detailed ways

In order to make the purpose, technical solutions, and advantages of this application clearer and clearer, the following further describes the application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application. Based on the examples in this application, all other examples obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of this application.

Obviously, the drawings in the following description are only some examples or embodiments of the application. For those of ordinary skill in the art, without creative work, the application can be applied to the application according to these drawings. Other similar scenarios. In addition, it can also be understood that although the efforts made in this development process may be complicated and lengthy, for those of ordinary skill in the art related to the content disclosed in this application, the technology disclosed in this application Some design, manufacturing or production changes made on the basis of the content are just conventional technical means, and should not be construed as insufficient content disclosed in this application.

Unless otherwise defined, the technical or scientific terms used in this application shall have the usual meanings understood by those with general skills in the technical field to which this application belongs. The "first", "second" and similar words used in the specification and claims of the patent application of this application do not indicate any order, quantity or importance, but are only used to distinguish different components. "One", "one", "one", "the" and other similar words do not mean limit of quantity, and may mean singular or plural.

"Including" or "including" and other similar words mean that the elements or items before "including" or "including" now cover the elements or items listed after "including" or "including" and their equivalent elements, and do not exclude Other components or objects.

Similar words such as "connected" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect.

The various technologies described in this article can be used in various mobile communication systems, such as 2G, 3G, 4G, and 5G mobile communication systems and next-generation mobile communication systems, such as the Global System for Mobile communications (GSM) , Code Division Multiple Access (CDMA) system, Time Division Multiple Access (TDMA) system, Wideband Code Division Multiple Access (Wireless, abbreviated as WCDMA), Frequency Division Multiple Access (Frequency Division Multiple Addressing, FDMA) system, Orthogonal Frequency-Division Multiple Access (OFDMA) System, Single Carrier FDMA (SC-FDMA) System, General Packet Radio Service (General Packet Radio Service, GPRS) system, Long Term Evolution (LTE) system, 5G New Radio (NR) system, and other such communication systems. The various technologies described in this article can also be used in various other wireless communication systems, such as wireless local area network (Wireless Local Area Network, WLAN for short), WiMAX and other systems.

According to the statistical information of the channel state and the EXtrinsic Information Transfer (EXIT) analysis of the decoding process of the two users, this application determines that when Raptor encoding is performed according to the preset average code length, the goal is to minimize the signal-to-noise ratio Optimize the frequency distribution coefficients of the two-user rateless coding, thereby obtaining the optimal frequency distribution under all possible channel conditions. The use of rate-free coded user information transmission based on the optimal frequency distribution for uplink transmission of two users is compared to the solution in the related technology that needs to optimize the frequency distribution based on the current global channel state information, the embodiment of the present application does not need to know the current Channel state information can realize channel coding, thereby reducing system signaling overhead and making the throughput of the information transmission system closer to the theoretical limit.

The embodiments of the present application are particularly suitable for two-user uplink transmission based on rateless coding in a block fading distributed multi-antenna system.

It should be noted that the user in the embodiments of the present application refers to a sending node device that sends user information, and the sending node device may be a smart terminal or a relay device and other sending node devices that need to send user information.

Fig. 1 is a schematic diagram of the uplink transmission process of a two-user distributed multi-antenna system according to an embodiment of the present application. User i (i=1, 2) uses rateless coding to encode original information m _i of length K into a code of length N The word c _i . Here, the LDPC code with the code rate of R _p is used as the precoding of the rateless code, and then the degree distribution is

LT code of, where d _c is the maximum output degree, Ω _i,d and Ω _i,d are the probability that the degree of c _{i is equal to d.} Finally, user i (i=1, 2) modulates the _{rateless code c i to x i} , and sends it to each RRH covering the user through the antenna.

In the foregoing process, the degree distribution of the LT coding in the rateless coding is determined according to the method for optimizing the degree distribution of the rateless coding for uplink transmission of two users in the embodiment of the present application.

This embodiment provides a method for optimizing the frequency distribution of rateless coding for uplink transmission of two users. Fig. 2 is a flowchart of a method for optimizing the frequency distribution of rateless coding for uplink transmission of two users according to an embodiment of the present application. The process includes the following steps:

Step S200: According to the statistical information of the channel state and the external information transfer analysis of the decoding process of the two users, it is determined that when the Raptor coding is performed according to the preset average code length, the target of minimizing the signal-to-noise ratio is optimized, and the rateless coding of the two users is optimized The optimization problem of the degree distribution coefficient of.

As shown in FIG. 3, step S200 may include the following steps:

_{For example, the rate distribution Ω i} (x) of the rateless coding adopted by each user i (i=1, 2) is obtained by the following optimization method:

Step S200-1: External information analysis (EXIT) of the decoding process.

First, the LLR message is transmitted on the decoding picture of user 1:

Step S200-1-1: The LT input node passes the LLR message to the LDPC code graph check node, and the external information it carries is:

Where

Is the average external information transmitted from the LT output node to the input node in the l-1th iteration, α _1,d is the proportion of the input node with degree _{d in the LT decoding graph, d v} is the maximum degree of the input node of the LT code graph, and

Step S200-1-2: The external information that the LDPC check node sends back to the LT input node is:

Where ξ _d is the proportion of variable nodes with degree d in the LDPC code graph,

Is the ratio of the edges connected to the check node of degree j in the LDPC code graph, d′ _v is the maximum degree of the variable node in the LDPC code graph, and d′ _c is the maximum degree of the check node in the LDPC code graph;

Step S200-1-3: The external information that the LT input node transmits the message to the output node is:

Where

Is the proportion of edges connected to the input node of degree i, and d _v is the maximum degree of the input node;

Step S200-1-4: The external information returned by the LT output node to the LT input node is:

Where

Is the output external information of the MU detector, which is composed of the channel matrix H and the external information of the output node of user 2

Determine (I _DET1 = aI _out2 + b, where a and b are constants, which are determined by two endpoints, namely (0, I _DET1 (0; H)) and (1, I _DET1 (1; H)), where

I(.) means mutual information);

Step S200-1-5: External information transmitted from the output node of user 1 to the MU detector:

The transfer process of the external information of the user 2 is consistent with the transfer process of the user 1, as shown in step S200-2-1 to step S200-2-5.

In order to ensure the success of the second step of decoding on the LDPC decoding sub-picture,

The threshold must be exceeded before reaching the maximum number of iterations, expressed as:

Where l′ is the maximum number of iterations, the external information threshold

Calculated by the following formula:

Step S200-3: Optimize the degree distribution according to external information analysis. The code length of Raptor code is expressed as

among them

It is the average degree of the LT input node of user i when the channel matrix is H. The transmission of the two users is synchronized, that is

In this embodiment, the distribution space of the channel matrix H is discretized into Q cases: H _q , q=1,...,Q. The probability of each case is expressed as Pr(H _q ). Therefore, the average code length of the Raptor code under the channel condition is:

Approximately

among them

Is a constant independent of the channel matrix. C _i (H _q ,P) is the theoretical achievable rate of user i when the _{channel matrix is H q and the transmission power is P:}

Where R ₁ and R ₂ are the achievable rates of user 1 and user 2, then

Step S200-4: Determine the optimization problem, the optimization problem is listed as follows:

The constraints of the optimization problem include:

(1) The degree distribution of the edge of the output node of the LT code graph and the constraint condition C1:

(2) Decoding start condition C2 at the receiving end:

ω _i,1 >ε,i=1,2 (16)

(3) Decoding convergence condition C3 at the receiving end:

For all H _q , i=1, 2 (17)

(4) The constraint condition C4 of preset average code length:

Among them, P _th is the transmit power threshold;

Is a constant irrelevant to the channel matrix; {ω _i,d } is the degree distribution coefficient of the edge of the output node of the LT code graph of user i;

Is the variance of independent Gaussian white noise; d _c is the maximum degree of the edge of the output node of the LT code graph; ω _i,d is the degree distribution coefficient of the edge of the output node of the degree d in the LT code graph corresponding to user i; ε; Is a preset value greater than zero;

In order for the output node of the LT code graph corresponding to user i to return the external information of the input node of the LT code graph under the maximum number of iterations l';

Is the external information threshold; H _q is the channel matrix in the q-th case where the distribution space of the channel matrix H is discretized into Q cases, q=1,...,Q; K is the length of the original information; R _p is no rate The code rate of the LDPC code in the encoding; Pr(H _q ) is the probability that the channel matrix is H _q ; C(H _q , P _th ) is the channel matrix H _q and the theoretical reach of user i when the transmission power is P _th rate.

Among them, L is the minimum Raptor code length required to successfully transmit information of length K, that is, the preset average code length, expressed as:

Among the above constraints, C2 is the starting condition of the BP algorithm, where ε is a small amount greater than zero; C3 guarantees that the average degree at the input node is

When the degree distribution is {ω _i,d }, it can be successfully decoded under all channels; C4 comes from (9)(18), that is, the average code length is fixed at L.

Step S201: Solve the optimization problem, and determine the optimized degree distribution of the rateless coding of the two users.

The above optimization problem can be solved by any solution method in related technologies, such as genetic algorithm or differential evolution algorithm. In some of these embodiments, the differential evolution algorithm can be used to calculate the optimal solution of the above optimization problem, and then the degree distribution coefficients of the edges of the output node of the LT code graph corresponding to the optimal solution can be used to calculate the corresponding non-uniformity of the two users. The degree distribution of the LT code diagram of the rate code, for example, by the formula

The conversion obtains the optimal rateless code degree distribution Ω _i (x).

This embodiment also provides a rateless coding method for uplink transmission of two users. The rateless coding method is applied to two sending node devices for uplink transmission of user information to a distributed multi-antenna system under a block fading channel. Fig. 4 is a flow chart of a rateless coding method for two-user uplink transmission according to an embodiment of the present application. The process includes the following steps:

Step S200: According to the statistical information of the channel state and the external information transfer analysis of the decoding process of the two users, it is determined that when the Raptor coding is performed according to the preset average code length, the target of minimizing the signal-to-noise ratio is optimized, and the rateless coding of the two users is optimized The optimization problem of the degree distribution coefficient of;

Step S201: Solve the optimization problem, and determine the degree distribution of the optimized two-user rateless coding;

Step S202: According to the degree distribution of the rateless coding, the user information of the two users are respectively subjected to rateless coding.

Compared with the related technology that needs to optimize the degree distribution based on the current global channel state information, at least through the above steps S200 to S202, there is no need to know the current channel state information, which reduces the system signaling overhead, and makes the information transmission system The throughput is closer to the theoretical limit. In addition, at least one method for determining an optimization problem and a solution method are provided in the above-mentioned embodiments, and the optimization problem and its optimal solution can be quickly determined in combination with computer computing technology, thereby improving the implementation efficiency of the embodiments of the present application.

The above-mentioned two-user uplink transmission rateless coding method optimizes the degree distribution of the rateless code to be used by each user based on the statistical information of the channel state of the distributed multi-antenna system under the block fading channel based on external information transmission (EXIT) analysis , And then the user encodes the original information using the rate-free code under the degree distribution, modulates the codeword and sends it to the remote radio head (RRH), and then the RRH preprocesses the received signal to obtain the baseband signal and After quantizing the baseband signals, they are sent to the baseband processing unit (BBU) pool through the high-speed fronthaul link, and finally the baseband processing unit pool applies the belief propagation (BP) algorithm to jointly decompress and decode the received signals.

This embodiment also provides a two-user uplink transmission method, which is applied to a distributed multi-antenna system under a block fading channel. Fig. 5 is a flowchart of a two-user uplink transmission method according to an embodiment of the present application. The process includes the following steps:

Step S200: According to the statistical information of the channel state and the external information transfer analysis of the decoding process of the two users, it is determined that when the Raptor coding is performed according to the preset average code length, the target of minimizing the signal-to-noise ratio is optimized, and the rateless coding of the two users is optimized The optimization problem of the degree distribution coefficient of;

Step S201: Solve the optimization problem, and determine the degree distribution of the optimized two-user rateless coding;

Step S202: The two sending node devices respectively perform rateless coding on their respective user information according to the degree distribution of the rateless coding;

Step S203: The two sending node devices respectively modulate the encoded non-rate code into an uplink transmission signal, and send the uplink transmission signal to the remote radio head covering the sending node device;

Step S204: The distributed multi-antenna system receives uplink transmission signals from multiple remote radio heads, and obtains uplink transmission signals of two users;

Step S205: The remote radio head of the distributed multi-antenna system performs preprocessing and quantization processing on the uplink transmission signals of the two users respectively to obtain the quantized signals of the two users;

Step S206: The baseband processing unit pool of the distributed multi-antenna system performs soft demodulation on the quantized signal of the other user of the two users according to the decoding output of one user of the two users in the previous round of decoding process, Then the belief propagation algorithm is used for joint decoding, and the user information of the two users is obtained respectively.

In some of these embodiments, in step S206, the baseband processing unit pool performs soft demodulation on the quantized signal of another user with the initial decoding output of one user during the first round of decoding process of the pool of the baseband processing unit, where the initial decoding output is 1. .

The following describes and illustrates the application through preferred embodiments.

Fig. 6 is a flowchart of the process of joint decompression and decoding of the received signals of two users by the distributed multi-antenna system according to the preferred embodiment of the present application. The process includes the following steps:

Step S601: The preprocessor of RRH j, j=1, preprocesses the received signal to obtain a baseband signal:

among them

Is the baseband signal at RRH j, P is the transmit power of each user, n _j is the mean value at RRH j is 0, and the variance is

Independent Gaussian white noise. Next RRH quantizer quantizing a signal, as the number of quantization levels M = 2 ^b, where b is the number of quantization bits, the signal is quantized to obtain quantized signal y _j y _j, quantization rule is expressed as:

among them,

Is the quantization interval,

Is the quantized value. Finally, the RRH sends the obtained quantized signal to the baseband processing unit pool through the high-speed fronthaul link.

Step S602: The two-user detector (MU) in the baseband processing unit pool according to the quantized signal

And the output soft information LLR ^e [c _i ] of the decoder to calculate the log-likelihood ratio (LLR) _{of the output codeword c i of user i, expressed as:}

among them

It is 1 in the first round of decoding, and the subsequent decoding process is equal to

Among them, LLR ^e [c _i′ ] is the decoding output of other users in the previous round. Take the case of i=1, c _i =0, c _i′ =1 as an example, when c _i =0, c _i′ =1 is fixed, y ₁ and y ₂ are Gaussian distributions

Where [k ₁₁ ,k ₁₂ ] and [k ₂₁ ,k ₂₂ ] represent

with

The quantization interval.

Step S603: The baseband processing unit pool performs detection and decoding based on the BP algorithm.

This embodiment also provides a rateless code decoding method for two-user uplink transmission, which is applied to the baseband processing unit pool for the detection and decoding process based on the belief propagation algorithm. Among them, the rate-free codes of the uplink transmission of the two users are encoded by the rate-free coding method provided in the embodiment of the present application. FIG. 7 is a flowchart of a rateless code decoding method for uplink transmission of two users according to an embodiment of the present application. FIG. 8 is a schematic diagram of joint decoding of a baseband processing unit pool in a preferred embodiment of the present application, as shown in FIG. 7 and FIG. 8 , The process includes the following steps:

Step S701: For each of the two users, perform iterative decoding on the entire decoding graph until the average value of the log-likelihood ratio of the input node of each of the two users exceeds a preset threshold.

In this embodiment, iterative decoding (including the detector) is performed on the entire decoding graph until the average value of the LLR of each user's input node exceeds a certain exceeding threshold m _th , for example:

In the first round of the decoding iteration, the message is first transmitted on the decoding picture of user 1, as shown in the following steps 1 to 6:

Step 1: The message is transmitted from the input node i to the LDPC check node c:

Where o is the output node connected to the input node.

Step 2: The message sent by the verification node c back to the input node i is updated to:

In the formula, i'is the input node connected to the check node c except the input node i in the decoding graph.

The input node i transmits to step 3: The message of the output node o is updated to:

In the formula, o′ represents the output node other than o.

Step 4: The message sent by the output node o back to the input node i is updated to:

In the above formula, i′ represents the input node other than i,

Is the message sent by the output node o to the input node i in the lth iteration;

Is the message sent by the input node i to the output node o in the lth iteration; z _o is the LLR output by the MU detector, which can be calculated by formula (22).

Step 5: The message LLR ^e [c ₁ ] sent to the MU detector is expressed as:

Step 6: The LLR of input node i is:

Next, a decoding process similar to that of user 1 is performed on the Raptor decoding map of user 2, and at this point, a round of decoding iteration is completed.

Step S702: For each of the two users, iterative decoding is performed on the LDPC code pattern respectively until the decoding is correct or the maximum number of iterations is reached.

In this embodiment, when the average LLR of each user's input node exceeds the threshold m _th , each user independently performs iterative decoding on the LDPC code graph to eliminate residual errors. In the second step, each user independently performs iterative decoding on the LDPC code map. It is the same as steps 1 and 2 in the above step S701. According to the judgment output result, if the decoding is not correct, the iteration continues. If the decoding is correct or reaches the maximum The number of iterations t ends decoding.

This embodiment also provides a rateless coding device for uplink transmission of two users, which is applied to a sending node device, and the device is used to implement the above-mentioned rateless coding method for uplink transmission of two users. FIG. 9 is a structural block diagram of a rateless encoding device for uplink transmission by two users according to an embodiment of the present application. The rateless encoding device for uplink transmission by two users includes:

The determining module 91 is configured to determine the optimized frequency distribution of the two users of the non-rate coding according to the optimization method of the frequency distribution of the non-rate coding;

The rateless encoding module 92, coupled to the determining module 91, is configured to perform rateless encoding on the user information of the sending node device according to the degree distribution of the rateless encoding.

In some of the embodiments, the preset average code length is determined according to the statistical information of the channel state of the block fading channel.

In some of these embodiments, the optimization problems are listed as follows:

The constraints of the optimization problem include:

(1) The degree distribution of the edge of the output node of the LT code graph and the constraint condition C1:

(2) Decoding start condition C2 at the receiving end:

ω _i1 >ε,i=1,2

(3) Decoding convergence condition C3 at the receiving end:

For all H _q , i=1, 2

(4) The constraint condition C4 of preset average code length:

Among them, P _th is the transmit power threshold;

Is a constant irrelevant to the channel matrix; {ω _i,d } is the degree distribution coefficient of the edge of the output node of the LT code graph of user i;

Is the variance of independent Gaussian white noise; d _c is the maximum degree of the edge of the output node of the LT code graph; ω _i,d is the degree distribution coefficient of the edge of the output node of the degree d in the LT code graph corresponding to user i; ε; Is a preset value greater than zero;

In order for the output node of the LT code graph corresponding to user i to return the external information of the input node of the LT code graph under the maximum number of iterations l';

Is the external information threshold; H _q is the channel matrix in the q-th case where the distribution space of the channel matrix H is discretized into Q cases, q=1,...,Q; K is the length of the original information; R _p is no rate The code rate of the LDPC code in the encoding; Pr(H _q ) is the probability that the channel matrix is H _q ; C(H _q , P _th ) is the channel matrix H _q and the theoretical reach of user i when the transmission power is P _th Rate; L is the preset average code length of the Raptor code.

In some of the embodiments, the determining module 91 includes: a determining unit for determining the optimal solution of the optimization problem using a differential evolution algorithm; a computing unit, coupled to the determining unit, for determining the LT code pattern corresponding to the optimal solution Output the degree distribution coefficient of the edge of the node, and calculate the degree distribution of the LT code graph without the rate code corresponding to the two users.

This embodiment also provides a rateless code decoding device for two-user uplink transmission, which is applied to a distributed multi-antenna system under a block fading channel. The device is used to implement the above-mentioned two-user uplink transmission rateless code decoding method, wherein the rateless code used for the uplink transmission of the two users is encoded using the rateless coding method provided in the embodiment of the present application. FIG. 10 is a structural block diagram of a rateless code decoding device for uplink transmission of two users according to an embodiment of the present application. The rateless code decoding device for uplink transmission of two users includes:

The first decoding module 101 is used to perform iterative decoding on the entire decoding graph for each of the two users until the average value of the log-likelihood ratio of the input node of each of the two users exceeds the preset value Threshold

The second decoding module 102, coupled to the first decoding module 101, is configured to perform iterative decoding on the LDPC code pattern for each of the two users respectively until the decoding is correct or the maximum number of iterations is reached.

This embodiment also provides a distributed multi-antenna system, which is applied to a block fading channel. FIG. 11 is a schematic structural diagram of a distributed multi-antenna system according to an embodiment of the present application. The distributed multi-antenna system includes a plurality of remote radio heads 111 and a baseband processing unit pool 112, in which,

The remote radio head 111 is used to receive the uplink transmission signal and send the uplink transmission signal to the baseband processing unit pool 112 after preprocessing and quantization processing; wherein, the uplink transmission signal is based on the rate-free coding method provided by the embodiment of the present application. The user information of the user is obtained by rate-free coding and then modulation;

The baseband processing unit pool, coupled to the remote radio head 111, is used to perform soft demodulation of the quantized signal of the other user of the two users according to the decoding output of one user of the two users in the previous round of decoding process Then, the belief propagation algorithm is used for joint decoding, and the user information of the two users is obtained respectively.

In some of the embodiments, the baseband processing unit pool 112 is also used to perform soft demodulation on the quantized signal of another user with the initial decoding output of one user during the first round of decoding, where the initial decoding output is 1. .

FIG. 12 is a schematic diagram of a preferred structure of a distributed multi-antenna system according to an embodiment of the present application. In some of the embodiments, the baseband processing unit pool 112 includes a first decoding module 1121 and a second decoding module 1122, among which,

The first decoding module 1121 is used to iteratively decode the entire decoding graph for each of the two users until the average value of the log-likelihood ratio of the input node of each of the two users exceeds the preset threshold ；

The second decoding module 1122, coupled to the first decoding module 1121, is used to perform iterative decoding on the LDPC code pattern for each of the two users until the decoding is correct or the maximum number of iterations is reached.

This embodiment also provides a computer-readable storage medium on which computer program instructions are stored. When the computer program instructions are executed by a processor, the aforementioned two-user uplink transmission rateless encoding method is realized.

This embodiment also provides a computer-readable storage medium on which computer program instructions are stored. When the computer program instructions are executed by a processor, the foregoing two-user uplink transmission rateless code decoding method is realized.

In the several embodiments provided in this application, it should be understood that the disclosed system, device, or method may be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of modules or units is only a logical function division. In actual implementation, there may be other division methods, for example, multiple units or components may be combined or It can be integrated into another system, or some features can be ignored or not implemented. In addition, the displayed or discussed mutual coupling or direct coupling or communication connection may be indirect coupling or communication connection through some interfaces, devices or units, and may be in electrical, mechanical or other forms.

The units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of the embodiment.

In addition, the functional units in the various embodiments of the present application may be integrated into one processing unit, or each unit may exist alone physically, or two or more units may be integrated into one unit. The above-mentioned integrated unit can be implemented in the form of hardware or software functional unit.

If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer readable storage medium. Based on this understanding, the technical solution of the present application essentially or the part that contributes to the existing technology or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium , Including several instructions to make a computer device (which may be a personal computer, a server, or a network device, etc.) or a processor execute all or part of the steps of the methods in the various embodiments of the present application. The foregoing processor may include a central processing unit (CPU), or a specific integrated circuit (Application Specific Integrated Circuit, ASIC for short), or may be configured to implement one or more integrated circuits of the embodiments of the present application. The above-mentioned storage medium can be used for mass storage of data or instructions. For example and not limitation, the memory may include a hard disk drive (Hard Disk Drive, referred to as HDD), floppy disk drive, flash memory, optical disk, magneto-optical disk, magnetic tape, or Universal Serial Bus (Universal Bus, referred to as USB) drive or two A combination of one or more of these. Where appropriate, the storage may include removable or non-removable (or fixed) media. Where appropriate, the memory can be internal or external to the data processing device. In a particular embodiment, the memory is a non-volatile solid state memory. In certain embodiments, the memory includes read-only memory (ROM). Where appropriate, the ROM can be mask-programmed ROM, programmable ROM (PROM), erasable PROM (EPROM), electrically erasable PROM (EEPROM), electrically rewritable ROM (EAROM) or flash memory or A combination of two or more of these.

The technical features of the above embodiments can be combined arbitrarily. In order to make the description concise, all possible combinations of the technical features in the above embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, they should be It is considered as the range described in this specification.

The above-mentioned embodiments only express several implementation modes of the present application, and their description is relatively specific and detailed, but they should not be interpreted as a limitation on the scope of the patent application. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of this application, several modifications and improvements can be made, and these all fall within the protection scope of this application. Therefore, the scope of protection of the patent of this application shall be subject to the appended claims.

Claims (13)

1. A method for optimizing the frequency distribution of rateless coding for two-user uplink transmission, which is applied to a distributed multi-antenna system under a block fading channel, and is characterized in that the method includes:

   According to the statistical information of the channel state and the external information transfer analysis of the decoding process of the two users, it is determined that when the Raptor coding is performed according to the preset average code length, with the goal of minimizing the signal-to-noise ratio, the degree distribution of the two users' rateless coding is optimized Optimization problem of coefficients;

   Solve the optimization problem, and determine the optimized degree distribution of the rateless coding of the two users.
2. The method according to claim 1, wherein the preset average code length is determined according to the statistical information of the channel state of the block fading channel.
3. The method according to claim 1, wherein the optimization problem is listed as follows:

   

   The constraints of the optimization problem include:

   (1) The degree distribution of the edge of the output node of the LT code graph and the constraint condition C1:

   

   (2) Decoding start condition C2 at the receiving end:

   ω _i,1 >ε,i=1,2

   (3) Decoding convergence condition C3 at the receiving end:

   

   For all H _q , i=1, 2

   (4) The constraint condition C4 of preset average code length:

   

   Among them, P _th is the transmit power threshold;

   

   Is a constant irrelevant to the channel matrix; {ω _i,d } is the degree distribution coefficient of the edge of the output node of the LT code graph of user i;

   

   Is the variance of independent Gaussian white noise; d _c is the maximum degree of the edge of the output node of the LT code graph; ω _i,d is the degree distribution coefficient of the edge of the output node of the degree d in the LT code graph corresponding to user i; ε; Is a preset value greater than zero;

   

   In order for the output node of the LT code graph corresponding to user i to return the external information of the input node of the LT code graph under the maximum number of iterations l′;

   

   Is the external information threshold; H _q is the channel matrix in the q-th case where the distribution space of the channel matrix H is discretized into Q cases, q=1,...,Q; K is the length of the original information; R _p is no rate The code rate of the LDPC code in the encoding; Pr(H _q ) is the probability that the channel matrix is H _q ; C(H _q , P _th ) is the channel matrix H _q and the theoretical reach of user i when the transmission power is P _th Rate; L is the preset average code length of the Raptor code.
4. The method according to claim 1, wherein the solving the optimization problem and determining the optimized degree distribution of the two-user rateless coding comprises:

   Using a differential evolution algorithm to determine the optimal solution of the optimization problem;

   According to the degree distribution coefficient of the edge of the output node of the LT code graph corresponding to the optimal solution, the degree distribution of the LT code graph without the rate code corresponding to the two users is calculated.
5. A rateless coding method for two-user uplink transmission, which is applied to two sending node devices for uplink transmission of user information to a distributed multi-antenna system under a block fading channel, and is characterized in that it includes:

   According to the method for optimizing the frequency distribution of rateless coding according to any one of claims 1 to 4, determine the optimized frequency distribution of the rateless coding of the two users;

   According to the degree distribution of the rateless coding, rateless coding is performed on the user information of the two users respectively.
6. A two-user uplink transmission method, applied to a distributed multi-antenna system under a block fading channel, characterized in that the method includes:

   The distributed multi-antenna system receives uplink transmission signals from multiple remote radio heads to obtain the uplink transmission signals of the two users; wherein, the uplink transmission signal is based on the rateless coding method according to claim 5. The user information of the two users is obtained by rate-free coding and then modulation;

   The distributed multi-antenna system performs preprocessing and quantization processing on the uplink transmission signals of the two users respectively to obtain the quantized signals of the two users;

   The distributed multi-antenna system performs soft demodulation on the quantized signal of the other of the two users according to the decoding output of one of the two users in the previous round of decoding, and then uses The belief propagation algorithm performs joint decoding to obtain the user information of the two users respectively.
7. The method according to claim 6, characterized in that, in the first round of decoding, the quantized signal of the other user is soft-demodulated using the initial decoding output of the one user, wherein the initial decoding The output is 1.
8. A rateless code decoding method for two-user uplink transmission, applied to a distributed multi-antenna system under a block fading channel, characterized in that the two-user uplink transmission adopts the two-user uplink transmission described in claim 6 or 7. Transmission method, the rate-free code decoding method for uplink transmission of two users includes:

   For each of the two users, iterative decoding is performed on the entire decoding graph until the average value of the log-likelihood ratio of the input node of each of the two users exceeds a preset threshold;

   For each of the two users, iterative decoding is performed on the LDPC code pattern respectively until the decoding is correct or the maximum number of iterations is reached.
9. A rateless coding device for two-user uplink transmission, which is applied to a sending node device, and is characterized in that the device includes:

   A determining module, configured to determine the optimized degree distribution of the two users of the rateless coding according to the method for optimizing the degree distribution of the rateless coding according to any one of claims 1 to 4;

   The rateless coding module is configured to perform rateless coding on the user information of the sending node device according to the degree distribution of the rateless coding.
10. A rateless code decoding device for two-user uplink transmission, which is applied to a distributed multi-antenna system under a block fading channel, characterized in that the two-user uplink transmission adopts the two-user uplink transmission described in claim 6 or 7. In the transmission method, the rateless code decoding device for uplink transmission of two users includes:

    The first decoding module is configured to perform iterative decoding on the entire decoding graph for each of the two users until the average value of the log likelihood ratio of the input node of each of the two users Exceed the preset threshold;

    The second decoding module is configured to respectively perform iterative decoding on the LDPC code pattern for each of the two users until the decoding is correct or the maximum number of iterations is reached.
11. A distributed multi-antenna system, the distributed multi-antenna system is applied to a block fading channel, characterized in that the distributed multi-antenna system includes a plurality of radio frequency remote heads and a pool of baseband processing units, wherein:

    The remote radio head is used to receive an uplink transmission signal and send the uplink transmission signal to the baseband processing unit pool after preprocessing and quantization processing; wherein the uplink transmission signal is according to claim 5 The rateless coding method is obtained by performing rateless coding on the user information of the two users and then modulating;

    The baseband processing unit pool is used to perform soft demodulation on the quantized signal of the other user of the two users according to the decoding output of one user of the two users in the previous round of decoding process, and then The belief propagation algorithm is used for joint decoding to obtain the user information of the two users respectively.
12. The distributed multi-antenna system according to claim 11, wherein the baseband processing unit pool is further configured to use the initial decoding output of the one user to send a message to the other user during the first round of decoding. The quantized signal is subjected to soft demodulation, wherein the initial decoding output is 1.
13. The distributed multi-antenna system according to claim 11, wherein the baseband processing unit pool includes a first decoding module and a second decoding module, wherein,

    The first decoding module is configured to perform iterative decoding on the entire decoding graph for each of the two users until the average value of the log likelihood ratio of the input node of each of the two users Exceed the preset threshold;

    The second decoding module is configured to respectively perform iterative decoding on the LDPC code pattern for each of the two users until the decoding is correct or the maximum number of iterations is reached.

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