A method and system for time slot allocation based on spatial multiplexing of underwater acoustic channel collision matrix

Abstract

The application discloses a kind of space multiplexing time slot allocation method and system based on underwater acoustic channel conflict matrix, first according to underwater acoustic transmission link model, the link signal receiving success probability in underwater acoustic network is calculated;Second, according to underwater network topology information and link signal receiving success probability, generate channel conflict matrix;Then, construct time slot allocation matrix is used to mark node occupies time slot situation, from time slot conflict situation, time slot occupancy and allocation uniformity angle, to time slot allocation construct multi-objective optimization function;Finally, according to underwater acoustic channel conflict matrix and time slot allocation matrix, through global search, find the optimal solution of time slot allocation.The application comprehensively considers the allocation of underwater channel resources from three aspects of time slot conflict, time slot utilization and time slot allocation uniformity, establishes an effective fitness evaluation mechanism, can make full use of channel resources, and improves underwater acoustic communication performance.

Description

TECHNICAL FIELD

[0001] The application relates to a space multiplexing time slot allocation method and system based on an underwater acoustic channel conflict matrix, in particular to a time slot allocation scheme for underwater network time division multiple access, and belongs to the technical field of communication. BACKGROUND

[0002] In marine research, establishing a high-reliability underwater acoustic communication network is the main means to obtain underwater information. The particularity of the underwater acoustic channel, such as high delay and narrow frequency band, brings many difficulties to the MAC protocol design of the underwater acoustic communication network. If these problems are not properly handled, an excellent underwater acoustic communication network cannot be built, and the limited channel resources cannot be fully utilized. Therefore, the research on the efficient MAC protocol of the underwater acoustic communication network is a key direction in marine technology. Most of the underwater acoustic communication network MAC protocols based on the improvement of TDMA have low adaptability. When facing the complex combination optimization problem of underwater channel resource allocation, the time slot allocation scheme cannot be considered from multiple angles, and often only a local optimal solution can be given. Secondly, the optimal time slot allocation scheme that fully utilizes the channel resources cannot be found in a short time.

[0003] Therefore, the main research topic of the application is to build an underwater time slot allocation scheme evaluation model, abstract the underwater time slot allocation scheme to a search sample space, find the optimal solution by using global search, realize space multiplexing on the basis of time division multiplexing, and fully utilize the channel resources. SUMMARY

[0004] The application provides a space multiplexing time slot allocation method and system based on an underwater acoustic channel conflict matrix, which models underwater time slot allocation, constructs a multi-factor evaluation system, evaluates the advantages and disadvantages of the time slot allocation scheme, generates a globally optimal time slot allocation result through global search, fully utilizes channel resources, and improves the performance of underwater acoustic communication.

[0005] The application provides a space multiplexing time slot allocation method based on an underwater acoustic channel conflict matrix, which comprises the following steps:

[0006] Step 1: According to the underwater acoustic transmission link model, the link signal reception success probability in the underwater acoustic network is calculated.

[0007] Step 2: According to the underwater network topology information and the link signal reception success probability, a channel conflict matrix is generated.

[0008] Third step: constructing time slot allocation matrix for marking node occupying time slot situation, constructing multi-objective optimization function for time slot allocation from time slot conflict situation, time slot occupancy rate and allocation uniformity; wherein time slot conflict situation is measured by sum of whether each node occupies each time slot conflicts, time slot occupancy rate is measured by reciprocal of average time slot number occupied by each node, wherein time slot allocation uniformity is measured by variance of each node time slot allocation number;

[0009] Fourth step: according to underwater acoustic channel conflict matrix and time slot allocation matrix, finding optimal solution of time slot allocation through global search.

[0010] As preferred, in the first step, according to underwater acoustic transmission link model, calculating signal receiving success probability of link in underwater acoustic network, including: according to bit error rate P e of actual underwater acoustic channel transmission model, calculating signal receiving success probability P s =1-P e ; according to underwater acoustic network topology, based on position information of node pair and underwater acoustic channel model, calculating signal receiving probability of link of the node pair, constructing underwater acoustic network receiving probability matrix P, size of which is N*N, wherein N is node number, matrix element takes value of signal receiving success probability P s of each pair of nodes.

[0011] As preferred, in the second step, according to position information of nodes of underwater network topology and link signal receiving success probability, generating channel conflict matrix, including:

[0012] Under the condition of known topology structure and actual link quality, according to position information of nodes, nodes with non-overlapping communication range share a time slot, first, generating preliminary channel conflict matrix according to topology and node information of network, its determination condition is:

[0013] Condition one: when a pair of node pairs exist mutual signaling conflict, then same time slot cannot be reused;

[0014] Condition two: when a pair of nodes exist signaling which will cause third party node conflict, then same time slot cannot be reused.

[0015] According to above two conditions, mapping actual position information and underwater acoustic link into preliminary channel conflict matrix based on maximum transmission range; when there are N nodes in network, then constructing an N*N preliminary channel conflict matrix A to represent; wherein element A ij takes 0 or 1, indicating whether node i and node j conflict with each other in signaling, when node i and node j exist mutual conflict in signaling, then A ij =1.

[0016] Secondly, according to the underwater acoustic network receiving probability matrix P and the preliminary channel conflict matrix A, a two-dimensional N*N actual channel conflict matrix C is constructed; wherein, when the node pair exists mutual conflict, it is explained that there is channel conflict, then C ij =1; when the node pair exists third party conflict, it is explained that it has probability channel conflict, and the probability is the sum of all potential conflict probabilities;

[0017]

[0018] Wherein, P ik , P jk are the link signal receiving success probabilities between node i and node k and between node j and node k respectively, A ik , A jk respectively indicate whether the corresponding nodes conflict with each other in signal transmission.

[0019] As preferred, the objective function f1 for optimizing time slot conflict is represented as:

[0020]

[0021] Wherein, indicates whether the node i occupies the jth time slot conflicts, T ij and T ik are the occupation conditions of node i to time slot j and k in the time slot allocation matrix, and the value 1 indicates occupation and 0 indicates non-occupation, C ik is the conflict condition of the ith node and the kth node in the channel conflict matrix.

[0022] As preferred, the objective function f2 for improving time slot utilization rate is represented as:

[0023]

[0024] Wherein, indicates the average number of time slots occupied by each node.

[0025] As preferred, the objective function f3 for improving time slot allocation uniformity is represented as:

[0026]

[0027] As preferred, the linear normalization method is adopted for de-dimensioning processing of the multi-objective function, and the linear weighting method is adopted for multi-objective optimization, and the constraint condition of the multi-objective optimization is to ensure that each time slot is allocated, and each node is allocated at least one time slot.

[0028] As preferred, in the fourth step, the encoding mapping mode of searching the sample space is that: the time slot allocation result is represented by time slot allocation matrix T, and is mapped into the sample vector in the form of binary encoding: assuming that there are M time slots allocated to N nodes, an N*M matrix is created, and the elements in the matrix are composed of 0 or 1, and the matrix is mapped into the sample vector in sequence according to column.

[0029] A computer system comprises a memory, a processor and a computer program / instruction stored on the memory and executable on the processor, and the computer program / instruction realizes the steps of the method when executed by the processor.

[0030] A computer program product comprises a computer program / instruction, and the computer program / instruction realizes the steps of the method when executed by the processor.

[0031] Beneficial effects: compared with the prior art, the technical scheme of the application has the following beneficial technical effects:

[0032] The method provided by the application realizes spatial multiplexing on the basis of time division multiplexing according to the underwater acoustic channel conflict matrix and the time slot allocation matrix, and fully utilizes channel resources; the generated time slot allocation scheme is evaluated by the fitness function, and the allocation of underwater channel resources is comprehensively considered from three aspects of time slot conflict, time slot utilization rate and time slot allocation uniformity; the underwater time slot allocation search sample space is constructed, the globally optimal time slot allocation result is generated through global search, the network throughput is improved, the end-to-end delay is reduced, the packet loss rate is reduced, and the network stability and reliability are improved. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 The flowchart of the application. DETAILED DESCRIPTION

[0034] The application will be further described below in combination with the drawings and specific embodiments.

[0035] As Figure 1 shown, the method disclosed by the embodiment of the application mainly comprises the following steps:

[0036] First step: according to the underwater acoustic transmission link model, the link signal reception success probability in the underwater acoustic network is calculated.

[0037] The channel attenuation of the underwater acoustic signal with a modulation frequency of f along the straight line transmission distance d is represented as:

[0038] A(d,f)=A0d ka(f) d #(1)

[0039] where A0 is a normalization factor, k represents the geometry of propagation, k = 1 represents cylindrical propagation, and k = 2 represents spherical propagation; a(f) represents the absorption exponent of underwater sound in the sea. The attenuation is expressed in dB form, which can be written as:

[0040]

[0041] In the above expression, the signal attenuation can be divided into two parts. The former term, which only has distance d as a variable, can be called the spreading loss, and the latter term, which involves frequency f, is called the absorption loss.

[0042] The ocean noise is divided according to the source: ocean current noise N i (f), ship noise N s (f), wave noise N w (f), and thermal noise N th (f). The main frequency band of the ocean current noise is within 10 Hz at a lower frequency; between 10-100 Hz, the noise generated by ship activities is the main noise; in the 100-100 kHz frequency band, the wave is the main influencing factor of the environmental noise, and the modeling object involves the wind speed w in addition to the frequency; above 100 kHz, thermal noise dominates. The expression of the total environmental noise of the entire network is:

[0043] N(f) = N i (f) + N s (f) + N w (f) + N th (f) #(3)

[0044] Based on the attenuation model of the underwater acoustic channel and the environmental noise model of the ocean, the narrowband underwater acoustic signal received signal-to-noise ratio SNR is expressed as:

[0045]

[0046] where P tx represents the transmitted power, and Δf represents the frequency band width.

[0047] According to the Rayleigh channel model, the system received error rate is:

[0048]

[0049] Therefore, the probability of successful signal reception is

[0050] P s = 1 - P e (d, f) #(6)

[0051] According to the underwater acoustic network topology, based on the position information of the node pair and the underwater acoustic channel model, the signal receiving probability of the node pair link is calculated, the underwater acoustic network receiving probability matrix P is constructed, and the matrix element takes the signal receiving success probability P of each pair of nodes s .

[0052] Second step: according to the position information of the underwater network topology node and the link signal receiving success probability, generate channel conflict matrix C. In the case of known topology structure and actual link quality, according to the position information of the node, the nodes with non-overlapping communication range share a time slot. First, generate the preliminary channel conflict matrix according to the topology and node information of the network, and the judgment condition is:

[0053] Condition one: when a pair of node pairs exist mutual signaling conflict, the same time slot cannot be reused;

[0054] Condition two: when a pair of nodes exist signaling that will cause third-party node conflict, the same time slot cannot be reused.

[0055] According to the above two conditions, the actual position information and the underwater acoustic link are mapped into the preliminary channel conflict matrix based on the maximum transmission range. When there are N nodes in the network, an N*N preliminary channel conflict matrix A is constructed to represent it. Among them, in the preliminary channel conflict matrix, the element A ij only takes 0 or 1, indicating whether node i and node j conflict with each other in signaling. When node i and node j exist mutual conflict in signaling, A ij =1.

[0056] Secondly, according to the underwater acoustic network receiving probability matrix P and the preliminary channel conflict matrix A, a two-dimensional N*N actual channel conflict matrix C is constructed. When a pair of nodes exist mutual conflict, it means that there is channel conflict, so C ij =1. When there is third-party conflict between a pair of nodes, it means that there is a probability of channel conflict, and the probability is the sum of all potential conflict probabilities.

[0057]

[0058] Third step: in the third step, from the perspective of time slot conflict, time slot occupancy rate and allocation uniformity, the time slot allocation is modeled, and a multi-factor evaluation system is constructed through multi-objective optimization to evaluate the pros and cons of the time slot allocation scheme. In this embodiment, a time slot allocation matrix is constructed to mark the node occupying time slot, and a multi-objective optimization function is constructed for time slot allocation from the perspective of time slot conflict, time slot occupancy rate and allocation uniformity. The time slot conflict is measured by counting the sum of whether each node occupies each time slot, and the time slot occupancy rate is measured by the reciprocal of the average number of time slots occupied by each node, and the time slot allocation uniformity is measured by the variance of the number of time slots allocated to each node.

[0059] Firstly, the time slot allocation scheme is modeled, and a two-dimensional N*M time slot allocation matrix T is constructed according to the node occupying time slot. Wherein, N is the number of nodes to be allocated, M is the number of allocatable time slots, t ij is 1 or 0, T ij =1 indicates that node i occupies time slot j to transmit, t ij =0 indicates that node i does not occupy time slot j to transmit. Secondly, for the time slot conflict, time slot utilization rate and allocation uniformity faced by the time slot allocation problem, multi-objective optimization is adopted to comprehensively consider the relationship among the three to optimize the time slot allocation result.

[0060] Time slot conflict: according to the channel conflict matrix and the time slot allocation matrix, it can be judged whether there is a conflict allocation in the time slot allocation matrix T, and the receiving conflict probability is calculated based on the receiving probability matrix. The objective function of optimizing the time slot conflict is constructed, the receiving conflict occurrence under the time slot allocation scheme is calculated based on the node receiving probability matrix, and then the time slot conflict under the time slot allocation scheme is optimized. The optimization objective function reflects the time slot conflict, which calculates the time slot occupation of the population individual and the receiving conflict of the network topology. Assuming that there are M time slots and N nodes in the network, define R ij to represent whether the i th node occupies the j th time slot conflicts, as shown in formula 8, wherein T ik represents the occupation of the i th node to the k th time slot in the time slot allocation matrix, C ik represents the conflict between the i th node and the k th node in the channel conflict matrix.

[0061]

[0062] Therefore, in the time slot allocation, the time slot conflict probability is reduced, and the objective function f1 of optimizing the time slot conflict is as follows:

[0063]

[0064] Wherein, T ij and T ikCij is the occupation of node i to time slot j and k in time slot allocation matrix, T ik Mik is the conflict of node i to node k in channel conflict matrix, C

[0065] Time slot occupation rate: X is defined as the uniformity of time slot allocation in the whole network, to evaluate the time slot occupation rate of time slot allocation scheme. The objective function of optimizing time slot utilization rate reflects the average number of time slots occupied by each node. The optimization objective function reflects the time slot utilization rate of the allocation scheme, which is calculated based on the time slot allocation matrix. The number of time slots occupied by each node X i . Then the average number of time slots occupied by each node is:

[0066]

[0067] Where T ij represents the occupation of the i-th node to the j-th time slot. The larger the better, where X i > 1, that is, each node will be allocated at least one time slot. Therefore, the objective function f2 of improving time slot utilization rate is:

[0068]

[0069] Allocation uniformity: S 2 is defined as the variance of the uniformity of time slot allocation in the whole network, to measure the uniformity of time slot allocation in the whole network. In order to make the uniformity of the number of time slots occupied by nodes in the time slot allocation scheme, the optimization objective function should be calculated based on the variance of the number of time slots. The calculation formula is as follows:

[0070]

[0071] S 2 The smaller the variance of the uniformity of time slot allocation, the more uniform the time slot allocation. Then the objective function f3 of improving the uniformity of time slot allocation is:

[0072]

[0073] In summary, the optimization function is established for different objectives of underwater time slot allocation, which is calculated by time slot allocation matrix T and channel conflict matrix C. The time slot allocation scheme should be constrained by the allocation of time slots and nodes, and should ensure that each time slot is allocated and each node is allocated at least one time slot. Therefore, the underwater time slot allocation function model is as follows:

[0074]

[0075] The constraint condition is:

[0076]

[0077] By linear normalization method, the objective function is de-dimensioned, and the value distribution is in [0, 1], and the original objective function will not change the value range because of linear transformation.

[0078] Firstly, the maximum value of each objective function in H time slot allocation schemes is defined as f i,max and f i,min respectively. i,max i,min The 3*H objective functions are de-dimensioned by f i,max and f i,min , and the processed objective functions are as follows:

[0079]

[0080] The value of the normalized objective function is distributed in [0, 1], and the original objective function will not change the value range because of linear transformation.

[0081]

[0082] Wherein, L is the number of objective functions, W i is the weighting coefficient of the objective function f i ', and W i is greater than or equal to 0, T1, T2,..., T H is the range where the minimum value of the objective function F is located.

[0083]

[0084] Since the optimization direction is positive, the reciprocal of F is defined as the fitness function, and G>0, as follows:

[0085]

[0086] Wherein f1' is the objective function of quantized time slot conflict, f2' is the objective function of time slot utilization rate, f3' is the objective function of time slot allocation uniformity, and W1, W2 and W3 are the weight ratio of the three objective functions.

[0087] Fourth step: according to the underwater acoustic channel conflict matrix and the time slot allocation scheme evaluation model, the coding mapping constructs the underwater time slot allocation search sample space, and the optimal solution of the time slot allocation is found through global search;

[0088] The embodiments of the present application are further described below in combination with examples:

[0089] (1) Configure the initialization of the underwater acoustic network.

[0090] (2) According to the underwater acoustic transmission link model, the link signal reception success probability in the underwater acoustic network is calculated. Then, according to the underwater network topology information and the link signal reception success probability, a channel conflict matrix is generated.

[0091] (3) From the time slot conflict situation, time slot occupancy rate and allocation uniformity, the time slot allocation is modeled, a multi-factor evaluation system is constructed through multi-objective optimization, and the advantages and disadvantages of the time slot allocation scheme are evaluated. For the time slot conflict, time slot utilization rate and allocation uniformity faced by the time slot allocation problem, multi-objective optimization is adopted, and the relationship among the three is comprehensively considered to optimize the time slot allocation result.

[0092] Suppose that there are H time slot allocation matrices in total, denoted as {T1, T2,..., TH}, according to the above formula, the values of the optimized time slot conflict objective function f1 of each time slot allocation matrix are {f1, f2,..., fH}, then the maximum value and the minimum value among these values are selected, and f1 is de-dimensioned by using f1 and fH. Similarly, the time slot utilization rate objective function f2 and the time slot allocation uniformity objective function f3 are de-dimensioned respectively. H 11 12 1H 1,max 1,min

[0093] (4) According to the underwater time slot allocation scheme, the search sample space is generated under the constraint condition by abstracting to a sample vector and performing encoding mapping. The time slot allocation result is represented by a time slot allocation matrix T, and is mapped into a sample vector in the form of binary coding. Assuming that M time slots are allocated to N nodes, an N*M matrix is created, the elements in the matrix are composed of 0 or 1, and the matrix is mapped into a sample vector in sequence from the 1st column, the 2nd column,..., the Mth column.

[0094] According to the underwater acoustic channel conflict matrix and the time slot allocation scheme evaluation model, the optimal solution of the time slot allocation is searched through global search. The global search algorithm can adopt simulated annealing algorithm, particle swarm algorithm and genetic algorithm, etc.

[0095] The computer system disclosed by the embodiment of the application comprises a memory, a processor and a computer program / instruction stored on the memory and capable of running on the processor, and the computer program / instruction is executed by the processor to realize the steps of the space multiplexing time slot allocation method based on the underwater acoustic channel conflict matrix.

[0096] The computer program product disclosed by the embodiment of the application comprises a computer program / instruction, and the computer program / instruction is executed by the processor to realize the steps of the space multiplexing time slot allocation method based on the underwater acoustic channel conflict matrix.​​​​​​

[0097] The above detailed description of the embodiments of the present application is made with specific examples applied to the principles and implementation manners of the present application. The above description of the embodiments is only used to help understand the method of the present application and its core idea. Meanwhile, for those skilled in the art, according to the idea of the present application, the specific implementation manners and application ranges will be changed. In summary, the content of the specification should not be understood as a limitation of the present application.

Claims

1. A spatial multiplexing time slot allocation method based on an underwater acoustic channel conflict matrix, characterized by: The following steps are involved: Step 1: Calculate the probability of successful link signal reception in the underwater acoustic network based on the underwater acoustic transmission link model; Step 2: Generate a channel conflict matrix based on the underwater network topology information and the probability of successful link signal reception; including: when the topology structure and actual link quality are known, let the nodes with non-overlapping communication ranges share a time slot based on the node location information. First, generate a preliminary channel conflict matrix based on the network topology and node information, and its judgment conditions are as follows: Condition 1: When a pair of nodes have a mutual signal conflict, they cannot reuse the same time slot; Condition 2: When a pair of nodes has a signal that will cause a conflict with a third-party node, they cannot reuse the same time slot; According to the above two conditions, the actual position information and the underwater acoustic link are mapped into a preliminary channel conflict matrix based on the maximum transmission range; When there are N nodes in the network, a preliminary channel conflict matrix A of N*N is constructed to represent it; Among them, the elements It takes 0 or 1, indicating whether node i and node j conflict with each other in sending messages. If node i and node j conflict with each other in sending messages, then ; Secondly, according to the underwater acoustic network reception probability matrix P and the preliminary channel conflict matrix A, a two-dimensional N*N actual channel conflict matrix C is constructed; among them, when there is a conflict between node pairs, it means that there is a channel conflict, then ;When there is a third-party conflict between a pair of nodes, it means that there is a probabilistic channel conflict, and its probability is the sum of all potential conflict probabilities; ； in 、 are the success probability of receiving link signals between node i and node k, and between node j and node k, respectively. 、 Respectively indicate whether the corresponding nodes conflict with each other in sending signals; Step 3: Construct a time slot allocation matrix to mark the time slot occupation of nodes. From the perspectives of time slot conflict, time slot occupancy rate and allocation uniformity, construct a multi-objective optimization function for time slot allocation. The time slot conflict is measured by summing up the number of conflicts among the time slots occupied by each node. The time slot occupancy rate is measured by the inverse of the average number of time slots occupied by each node. The time slot allocation uniformity is measured by the variance of the number of time slots allocated to each node. The objective function for optimizing time slot conflict is Expressed as: ； in, , indicating whether node i occupies the jth time slot or not, and is the occupancy of time slots j and k by node i in the time slot allocation matrix, with a value of 1 indicating occupation and 0 indicating non-occupancy. is the conflict between the i-th node and the k-th node in the channel conflict matrix, M is the number of time slots, and N is the number of nodes; Objective function to improve time slot utilization Expressed as: ； in, represents the average number of time slots occupied by each node; Objective function to improve time slot allocation uniformity Expressed as: ； Step 4: Based on the underwater acoustic channel conflict matrix and the time slot allocation matrix, find the optimal solution for time slot allocation through global search.

2. The method for allocating time slots for spatial multiplexing based on an underwater acoustic channel conflict matrix according to claim 1, characterized in that: In the first step, the probability of successful link signal reception in the underwater acoustic network is calculated based on the underwater acoustic transmission link model, including: the bit error rate according to the actual underwater acoustic channel transmission model , the probability of successful signal reception is calculated as According to the underwater acoustic network topology, based on the location information of the node pair and the underwater acoustic channel model, the signal reception probability of the node pair link is calculated, and the underwater acoustic network reception probability matrix P is constructed. Its size is N*N, where N is the number of nodes, and the matrix elements are the signal reception success probability of each pair of nodes. .

3. The method for allocating time slots for spatial multiplexing based on an underwater acoustic channel conflict matrix according to claim 1, characterized in that: The linear normalization method is used to dedimensionalize the multi-objective function, and the linear weighting method is used to achieve multi-objective optimization. The constraints of the multi-objective optimization are to ensure that each time slot is allocated and each node is allocated at least one time slot.

4. The method for allocating time slots for spatial multiplexing based on an underwater acoustic channel conflict matrix according to claim 1, characterized in that: In the fourth step, the coding mapping method of the search sample space is as follows: the time slot allocation result is represented by the time slot allocation matrix T, and it is mapped to the sample vector in the form of binary coding: assuming that there are M time slots allocated to N nodes, then create an N*M matrix with elements consisting of 0 or 1, and map the matrix to the sample vector column by column.

5. A computer system comprising a memory, a processor, and a computer program / instruction stored in the memory and executable on the processor, wherein: When the computer program / instructions are executed by a processor, the steps of the spatial multiplexing time slot allocation method based on the underwater acoustic channel conflict matrix according to any one of claims 1 to 4 are implemented.

6. A computer program product comprising a computer program / instructions, characterized in that When the computer program / instructions are executed by a processor, the steps of the spatial multiplexing time slot allocation method based on the underwater acoustic channel conflict matrix according to any one of claims 1 to 4 are implemented.

Images