CN113364517B - Asynchronous access-oriented satellite Internet of things terminal identity identification method - Google Patents

Abstract

The invention discloses a satellite Internet of things terminal identity identification method facing asynchronous access, which comprises three parts of terminal identity sequence receiving, time delay matching and identity detection and user terminal offset. The terminal identity sequence receiving is that superposition of Reed-Muller sequences and noise of a plurality of users is received under the asynchronous condition; the time delay matching and the identity detection are to use an algorithm to carry out the time delay matching and the identification of the user identity on the received signals; the user terminal offsets the received signal, subtracts the terminal user identity sequence detected under the matched time delay, offsets, then puts the obtained sequence into the time delay matching and identity detection for iteration, and finally sets a decision threshold through energy detection for ending the iteration.

Description

Asynchronous access-oriented satellite Internet of things terminal identity identification method

Technical Field

The invention relates to the technical field of satellite communication, in particular to an asynchronous access-oriented satellite internet of things terminal identity identification method.

Background

With the continuous development of human society, the requirements of information and networks are higher and higher, information communication is performed all the time around the world, most of current communication depends on ground wireless communication, when terminals are far away or in complex environments such as remote mountainous areas, poor communication quality or even communication failure may be caused by light on the ground communication, the existing ground wireless communication cannot meet the requirements of people on information acquisition, and people begin to explore other fields, such as the satellite communication field. The satellite communication has the characteristics of wide coverage range, no limitation by geography, climate factors and natural disasters and the like, has great strategic significance in aspects of maintaining national security, promoting economic development and the like, and is increasingly researched at present.

As the 4G era advances to the 5G era, key technical indicators of communication frequency bands, application requirements, technical standards, and the like of the 5G era are determined successively, wherein a Massive internet of things service (mtc) oriented to connection is an important application scenario of the 5G communication system. The concept of the internet of things is improved gradually from the point of presentation to the present, and the application of the internet of things relying on wireless local area networks such as the traditional ground cellular network is gradually developed and matured, but the traditional ground internet of things cannot be realized in some regions due to the limitation of factors such as space and environment. The satellite communication system can provide access service for the Internet of things terminal placed in remote areas by virtue of the characteristics of wide coverage range, no limitation of geography, climate factors, natural disasters and the like, and can realize real 'everything interconnection' in the global range.

The rapid development of the satellite internet of things technology brings great challenges to the satellite communication technology, and how to guarantee the service quality of users and how to meet the requirement of large-scale user access is a problem which needs to be solved urgently. The large-scale machine communication service traffic, automation, medical treatment, industry, agriculture and other industries promote the revolution of social production modes. While the random access process is the key to realize large-scale connection, under the condition of large-scale connection, frequent collision and sudden retransmission can cause network congestion, delay increase and resource waste. To reduce congestion and achieve low latency, this process must be done with high accuracy and low complexity. In general, detection of active users from tens or hundreds of user sequence spaces can be achieved through careful sequence design and exhaustive sequence search, however, in a large scale access scenario where the user sequence space may be as high as hundreds of thousands or even millions, it is very challenging to do so, and such detection is reminiscent of a large sea fishing needle. Because different active users transmit signals at different times, the sequence of users received by the access point is not synchronous, which increases the difficulty of correctly detecting multiple users in the received signals. On the one hand, given the large number of potential users in the system, it is not possible to assign orthogonal sequences to each user. On the other hand, non-orthogonal sequences will inevitably impose multi-user interference during detection. Therefore, a key challenge is to obtain a relatively large sequence space while obtaining reliable detection.

In the prior art, application publication No. CN107306394A discloses a method for acquiring cellular internet of things terminal information, which includes that a cellular internet of things terminal receives a request message for acquiring cellular internet of things terminal information, where the request message includes a service list for verifying whether an external application is authorized to acquire the cellular internet of things terminal information. The CIoT terminal can directly process the information acquisition request of the external application, thereby effectively reducing the network resource consumption and the signaling flow and reducing the network congestion on the basis of ensuring the information security of the CIoT terminal. It does not allow a relatively large sequence space.

Based on the above viewpoints, the terminal identity identification method of the satellite internet of things based on the asynchronous access, which is researched herein, selects the user sequence as a Reed-Muller sequence, and the Reed-Muller sequence has a large spatial order of magnitude, and can meet the requirement of mass communication. The user sequence may be uniquely and unambiguously mapped to the user identity. Thus, the access point can infer the user identity immediately upon correct detection of the user sequence. Meanwhile, the structural characteristics of the Reed-Muller sequence can be used for designing an efficient detection algorithm with low calculation complexity, a channel estimation coefficient can be obtained while a user sequence is detected, and the channel estimation step is not required to be called by adding extra calculation amount. In asynchronous detection, since the delay information is unknown, a genetic algorithm can be adopted to find the best matching delay.

Disclosure of Invention

In order to overcome the defects in the prior art, the invention provides a terminal identity identification method of a satellite internet of things facing asynchronous access, which realizes the requirement of large-scale user connection in satellite communication by adopting a Reed-Muller sequence as a user identity sequence, realizes low time delay by the low complexity of Reed-Muller sequence detection, and quickly finds the optimal matching time delay by an algorithm under the asynchronous condition. Finally, each active user identity sequence can be separated out in an asynchronous multi-user scene.

In order to achieve the purpose, the invention is realized by the following technical scheme:

the invention relates to an asynchronous access-oriented satellite Internet of things terminal identity identification method, which comprises three parts of terminal identity sequence receiving, time delay matching and identity detection and user terminal offset, and specifically comprises the following steps:

(1) receiving a terminal identity sequence: different users send Reed-Muller sequences at different time, and the sequences received by the access point are the superposition of a plurality of asynchronous Reed-Muller user sequences;

(2) time delay matching and identity detection: the method comprises two parts of time delay matching and user identity detection:

(2.1) time delay matching: setting a fitness function by taking parameters of user identity detection as a target function, reasonably configuring each parameter in a genetic algorithm, obtaining an individual with high fitness through a random competition selection method, single-point crossing and variation, and performing iteration for a certain number of times to obtain an optimal individual, namely optimal matching time delay;

(2.2) user identity detection: recovering a user identity sequence in a receiving sequence by utilizing a nested structure of a Reed-Muller sequence and a special Reed-Muller sequence mapping rule;

(3) user terminal cancellation: the method comprises two parts of user sequence cancellation and energy detection:

(3.1) cancellation of user sequences: subtracting the user sequence detected in (2) from the received sequence;

(3.2) energy detection: and (3) calculating the energy value of the received sequence, comparing with a decision threshold, if the energy value is greater than the decision threshold, indicating that a user identity sequence is not detected yet, then putting the received sequence obtained in the step (3.1) into the step (2) for iteration, and if the energy value is less than the decision threshold, indicating that the rest received sequences are noise sequences, and ending the iteration.

The invention is further improved in that: in the step (1), the formulas of the user identity sequence and the receiving sequence are as follows:

wherein: m is the order of the Reed-Muller sequence, the Reed-Muller sequence has a length of 2^m，C_jIs the jth symbol in the user identity sequence, b^mIs a (m × 1) column vector corresponding to the user ID, wt (-) represents the number of "1" in the vector, i.e. the code weight, P^mIs made byA (m x m) matrix corresponding to the subscriber identity,

is an m-bit binary expression of j-1; y is_jIs the jth symbol, δ, in the received sequence_maxIs the maximum time delay, k_maxIs the number of users, h_kIs the channel coefficient for the kth user, which is modeled as a complex gaussian random process with unit variance,

is the jth symbol, δ, in the Reed-Muller identity sequence of the kth user_kIs the delay value of the kth user and n represents complex additive white gaussian noise.

The invention is further improved in that: the optimal time delay matching is found by taking parameters in single user identity detection as an objective function, a scale transformation method is selected, the objective function is taken as a fitness function, then the fitness function is subjected to linear transformation, and the formula is as follows:

F′(X)＝α*Fit(X)+β

wherein: f' (X) is the fitness function after transformation, Fit (X) is the fitness function, Fit_avgDenotes the average value of Fit (X), Fit_minRepresents the minimum value of Fit (X), X is the time delay number;

carrying out the operation of eliminating the population to obtain a new population by a random competitive selection method, then carrying out single-point crossing to enable new individuals to appear in the new population, inheriting the basic characteristics of a parent, carrying out variation after crossing, determining the global search capability of the genetic algorithm by crossing, wherein the variation is only an auxiliary method for generating the new individuals, determining the local search capability of the genetic algorithm, and finally finding the optimal time delay matching after a certain number of iterations;

(2.2) firstly, designing a Reed-Muller matrix vector pair { P, b }, wherein P is a matrix, b is a column vector, then mapping the Reed-Muller matrix vector pair { P, b } into a unique Reed-Muller sequence, multiplying a Reed-Muller first half sequence and a Reed-Muller second half sequence to obtain a sequence, and orthogonal to a Walsh sequence, namely after the vector is multiplied by the Walsh matrix, a maximum value exists, and the rest values are all equal to 0, and by utilizing the characteristic, carrying out the above operation on a received sequence to obtain the position of the maximum value:

wherein w is the position of the maximum, (-)_IRepresenting the real part, V_iThe ith value after the received sequence and the Walsh sequence are multiplied by a matrix is represented, and the total value is m;

and w contains partial information of the matrix vector pair { P, b }, the matrix vector pair { P, b } is disassembled one layer each time by using a nested structure of a Reed-Muller sequence, namely the matrix P deletes a first row and a first column, partial information of the nested structure can be recovered each time, and finally the matrix vector pair { P, b } can be completely recovered by adding the matrix P one by one, and meanwhile, a channel coefficient corresponding to the detected user can be obtained, and the matrix vector pair { P, b } and the Reed-Muller sequence are in one-to-one correspondence, so that the user identity can be obtained. The invention is further improved in that: the step (3) specifically comprises the following steps:

(3.1) subtracting the detected user sequence, channel estimation coefficient and corresponding time delay from the received sequence in step (2) to reduce the interference to the undetected user, wherein the formula is as follows:

wherein: y is the receiving orderColumn, delta_iIndicating the delay of the current detection of the ith user,

indicating that the channel estimation coefficient corresponding to the ith user is currently detected,

indicating the currently detected ith user sequence;

(3.2) calculating the energy of the received sequence after the cancellation in (3.1), if the energy value is less than the decision threshold, it indicates that all the user identities have been detected, if the energy value is greater than the decision threshold, then jumping to the step (2) to continue detecting the user identity sequence until the energy value is less than the decision threshold, and the energy value calculation formula is as follows:

where E is the energy of the received sequence, y (i) is the ith symbol in the received sequence, and y (i) is a sequence of complex numbers.

The invention has the beneficial effects that: according to the asynchronous access-oriented satellite Internet of things terminal identity identification method, the unique Reed-Muller user identity sequence is generated through the matrix vector pair, the user sequence space is expanded, the method can be used for large-scale random access, and the sequence space is exponentially multiplied along with the code length. Meanwhile, aiming at the asynchronous multi-user condition, a genetic algorithm is provided to obtain the optimal time delay matching, the optimal time delay can be estimated under the condition that the time delay is unknown, and then the user identity sequence is detected. The problem that the terminal identity is difficult to detect correctly under the asynchronous condition of the satellite is solved.

Drawings

FIG. 1 is a flow chart of the present invention.

Fig. 2 is a relationship curve between the signal-to-noise ratio and the detection success probability for different users.

Detailed Description

In the following description, for purposes of explanation, numerous implementation details are set forth in order to provide a thorough understanding of the embodiments of the invention. It should be understood, however, that these implementation details are not to be interpreted as limiting the invention. That is, in some embodiments of the invention, such implementation details are not necessary.

The technical scheme of the invention is further explained in detail by combining the attached drawings:

as shown in fig. 1-2, the invention relates to a terminal identity identification method of a satellite internet of things facing asynchronous access, which comprises three parts of terminal identity sequence receiving, time delay matching and identity detection and user terminal offset, and comprises the following specific steps:

(1) receiving a terminal identity sequence: different users send Reed-Muller sequences at different time, and the sequences received by the access point are the superposition of a plurality of asynchronous Reed-Muller user sequences;

the formula of the user identity sequence and the receiving sequence is as follows:

wherein: m is the order of the Reed-Muller sequence, the Reed-Muller sequence has a length of 2^m，C_jIs the jth symbol in the user identity sequence, b^mIs a (m × 1) column vector corresponding to the user ID, wt (-) represents the number of "1" in the vector, i.e. the code weight, P^mIs a matrix of (m x m) corresponding to the user identity,

is an m-bit binary expression of j-1; y is_jIs the jth symbol, δ, in the received sequence_maxIs the maximum time delay, k_maxIs the number of users, h_kIs the k < th > oneThe channel coefficients of the user, which are modeled as complex gaussian random processes with unit variance,

is the jth symbol, δ, in the Reed-Muller identity sequence of the kth user_kIs the time delay value of the kth user, n represents the complex additive white gaussian noise;

(2) time delay matching and identity detection: the method comprises two parts of time delay matching and user identity detection:

(2.1) time delay matching: in the current scenario, the information of the time delay is unknown, so that the optimal time delay matching is found by using the parameter in the single user identity detection as the objective function, because the objective function value can be positive or negative and the maximum and minimum values cannot be estimated, a scale transformation method is selected, the objective function is used as a fitness function, and then the fitness function is linearly transformed, and the formula is as follows:

F′(X)＝α*Fit(X)+β

wherein: f' (X) is the fitness function after transformation, Fit (X) is the fitness function, Fit_avgDenotes the average value of Fit (X), Fit_minRepresents the minimum value of Fit (X), X is the time delay number;

then, performing a win-win and loss-elimination operation on the population by a random competition selection method, wherein the probability of selecting the individual with high fitness is high, the probability of selecting the individual with low fitness is low, a new population can be obtained, then, the new population is subjected to single-point crossing, so that a new individual appears in the new population, the new individual can inherit the basic characteristics of a parent, mutation is performed after crossing, the global search capability of the genetic algorithm is determined by crossing, the mutation is only an auxiliary method for generating the new individual, the local search capability of the genetic algorithm is determined, and finally, the optimal time delay matching can be found after a certain number of iterations;

(2.2) user identity detection: firstly, designing a matrix vector pair { P, b } of Reed-Muller, wherein P is a matrix, b is a column vector, then mapping the matrix vector pair and the Reed-Muller sequence into a Reed-Muller sequence, wherein the matrix vector pair and the Reed-Muller sequence are in one-to-one correspondence, and thus, a sequence obtained by multiplying a Reed-Muller first half sequence and a Reed-Muller second half sequence is orthogonal to a Walsh sequence, namely after the vector and the Walsh matrix are multiplied, a maximum value exists, and the rest values are all equal to 0, and by using the characteristic, the received sequence can be subjected to the above operation to obtain the position of the maximum value:

wherein w is the position of the maximum, (-)_IRepresenting the real part, V_iM values representing the ith value obtained by multiplying the received sequence by the Walsh sequence matrix;

w contains partial information of the matrix vector pair { P, b }, the matrix vector pair { P, b } is disassembled one layer each time by using a nested structure of a Reed-Muller sequence, so that the partial information of the nested structure can be recovered each time, and finally, the matrix vector pair { P, b } can be completely recovered by adding one block layer by layer, and meanwhile, a channel coefficient corresponding to a detected user can be estimated, and the matrix vector pair { P, b } and the Reed-Muller sequence are in one-to-one correspondence relationship, so that the user identity can be obtained;

(3) user terminal cancellation: the method comprises two parts of user sequence cancellation and energy detection:

(3.1) cancellation of user sequences: by removing the user sequence, channel estimation coefficient and corresponding delay detected in step (2) from the received sequence, the interference to undetected users can be reduced, and the formula is as follows:

wherein: y is the receive sequence, δ_iIndicating the delay of the current detection of the ith user,

indicating that the channel estimation coefficient corresponding to the ith user is currently detected,

indicating the currently detected ith user sequence;

(3.2) energy detection: calculating the energy of the received sequence after the cancellation in the step (3.1), if the energy value is less than the decision threshold, it indicates that all the user identities have been detected, the iteration is finished, if the energy value is greater than the decision threshold, the step (2) is skipped to continue detecting the user identity sequence until the energy value is less than the decision threshold, and the energy value calculation formula is as follows:

where E is the energy of the received sequence, y (i) is the ith symbol in the received sequence, and y (i) is a sequence of complex numbers.

The above description is only of the preferred embodiments of the present invention, and it should be noted that: it will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the principles of the invention and these are intended to be within the scope of the invention.

Claims (4)

1. An asynchronous access-oriented satellite Internet of things terminal identity identification method is characterized by comprising the following steps: the method comprises three parts of terminal identity sequence receiving, time delay matching, identity detection and user terminal offset, and specifically comprises the following steps:

step (1), receiving a terminal identity sequence: different users send Reed-Muller sequences at different time, and the sequences received by the access point are the superposition of a plurality of asynchronous Reed-Muller user sequences;

step (2), time delay matching and identity detection: the method comprises two parts of time delay matching and user identity detection:

step (2.1) time delay matching: setting a fitness function by taking parameters of user identity detection as a target function, reasonably configuring each parameter in a genetic algorithm, obtaining an individual with high fitness through a random competition selection method, single-point crossing and variation, and performing iteration for a certain number of times to obtain an optimal individual, namely optimal matching time delay;

step (2.2) user identity detection: firstly, designing a Reed-Muller matrix vector pair { P, b }, wherein P is a matrix, b is a column vector, then mapping { P, b } into a unique Reed-Muller sequence, multiplying a Reed-Muller first half sequence and a Reed-Muller second half sequence to obtain a sequence, and orthogonal to a Walsh sequence, namely after the vector is multiplied by the Walsh matrix, a maximum value exists, and the rest values are equal to 0, and by utilizing the characteristic, performing the operation on a received sequence to obtain the position of the maximum value:

wherein w is the position of the maximum, (-)_IRepresenting the real part, V_iThe ith value after the received sequence and the Walsh sequence are multiplied by a matrix is represented, and the total value is m;

w contains partial information of the matrix vector pair { P, b }, the matrix vector pair { P, b } is disassembled one layer each time by using a nested structure of a Reed-Muller sequence, namely the matrix P deletes a first row and a first column, then partial information of the nested structure can be recovered each time, and finally the matrix vector pair { P, b } can be completely recovered by adding the matrix P one by one, and meanwhile, a channel coefficient corresponding to the detected user can be obtained, and the matrix vector pair { P, b } is in one-to-one correspondence with the Reed-Muller sequence, so that the user identity is obtained;

and (3) the user terminal counteracts: the method comprises two parts of user sequence cancellation and energy detection:

step (3.1) counteracting of user sequences: subtracting the user sequence detected in (2) from the received sequence;

step (3.2) energy detection: and (3) calculating the energy value of the received sequence after cancellation, then comparing the energy value with a decision threshold, if the energy value is greater than the decision threshold, indicating that a user identity sequence is not detected yet, then putting the received sequence obtained in the step (3.1) into the step (2) for iteration, if the energy value is less than the decision threshold, indicating that the rest received sequences are noise sequences, and ending the iteration.

2. The asynchronous access-oriented satellite internet of things terminal identity identification method according to claim 1, wherein the asynchronous access-oriented satellite internet of things terminal identity identification method comprises the following steps: in the step (1), the formulas of the user identity sequence and the receiving sequence are as follows:

wherein: m is the order of the Reed-Muller sequence, the Reed-Muller sequence has a length of 2^m，C_jIs the jth symbol in the user identity sequence, b^mIs a (m × 1) column vector corresponding to the user ID, wt (-) represents the number of "1" in the vector, i.e. the code weight, P^mIs a matrix of (m x m) corresponding to the user identity,

is an m-bit binary expression of j-1; y is_jIs the jth symbol, δ, in the received sequence_maxIs the maximum time delay, k_maxIs the number of users, h_kIs the channel coefficient for the kth user, which is modeled as a complex gaussian random process with unit variance,

is the jth symbol, δ, in the Reed-Muller identity sequence of the kth user_kIs the delay value of the kth user and n represents complex additive white gaussian noise.

3. The asynchronous access-oriented satellite internet of things terminal identity identification method according to claim 2, wherein the asynchronous access-oriented satellite internet of things terminal identity identification method comprises the following steps: the step (2.1) is specifically operated as follows: the optimal time delay matching is found by taking parameters in single user identity detection as an objective function, a scale transformation method is selected, the objective function is taken as a fitness function, then the fitness function is subjected to linear transformation, and the formula is as follows:

F′(X)＝α*Fit(x)+β

wherein: f' (X) is the fitness function after transformation, Fit (X) is the fitness function, Fit_avgDenotes the average value of Fit (X), Fit_minRepresents the minimum value of Fit (X);

carrying out the selection and elimination operation on the population by a random competition selection method to obtain a new population, carrying out single-point crossing to enable new individuals to appear in the new population, inheriting the basic characteristics of a parent, carrying out variation after crossing, determining the global search capability of the genetic algorithm by crossing, wherein the variation is only an auxiliary method for generating the new individuals, determining the local search capability of the genetic algorithm, and finally finding the optimal time delay matching after a certain number of iterations.

4. The asynchronous access-oriented satellite internet of things terminal identity identification method according to claim 3, wherein the asynchronous access-oriented satellite internet of things terminal identity identification method comprises the following steps: the step (3) specifically comprises the following steps:

(3.1) subtracting the detected user sequence, channel estimation coefficient and corresponding time delay from the received sequence in step (2) to reduce the interference to the undetected user, wherein the formula is as follows:

wherein: y is the receive sequence, δ_iIndicating the delay of the current detection of the ith user,

indicating that the channel estimation coefficient corresponding to the ith user is currently detected,

indicating the currently detected ith user sequence;

(3.2) calculating the energy of the received sequence after the cancellation in (3.1), if the energy value is less than the decision threshold, it indicates that all the user identities have been detected, if the energy value is greater than the decision threshold, then jumping to the step (2) to continue detecting the user identity sequence until the energy value is less than the decision threshold, and the energy value calculation formula is as follows:

where E is the energy of the received sequence, y (i) is the ith symbol in the received sequence, and y (i) is a sequence of complex numbers.

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