A self-organizing network method for jungle mobile communication

Abstract

The present invention belongs to the field of communication technology, and in particular to a self-organizing network method for jungle mobile communication; specifically, it is mainly divided into drawing corresponding communication topology diagrams according to formations corresponding to different situations; calculating the maximum reliable communication distance between groups; designing a link interference diagram corresponding to the communication topology; selecting a value method of a backoff factor according to the relationship between the queue length of a data packet and the threshold length to achieve a balance between delay performance and reliability; and achieving efficient communication in an extreme environment such as a jungle without a base station, ensuring reliable connection, and distributed access and transmission of nodes.

Description

Technical Field

[0001] The invention belongs to the technical field of communication, and in particular relates to a self-organizing network method for jungle mobile communication. Background Art

[0002] The jungle area is extremely sparsely populated. Considering cost and other issues, operators generally do not set up base stations and other communication infrastructure in the jungle. In this case, if an emergency occurs in the jungle and there is a need for communication, communication nodes can only communicate using wireless ad hoc networks. Due to the characteristics of electromagnetic wave propagation, the penetration of communication signals in Maolin area is poor, and the communication distance is limited. Communication nodes may "lose connection" with other nodes during movement, forming "islands". In wireless ad hoc networks, how nodes can flexibly form networks, ensure reliable connections, distributed access and transmit data are difficult problems in jungle wireless ad hoc networks. Summary of the invention

[0003] In order to overcome the above problems, the present invention provides a self-organizing network method for jungle mobile communication, which can achieve efficient communication in the extreme environment of jungle without base stations, ensure reliable connection, and distributed access and transmission of nodes.

[0004] A self-organizing network method for jungle mobile communication, comprising the following contents:

[0005] Step 1: Establish a connection relationship between communication nodes to form a communication topology graph;

[0006] According to the networking idea of ​​mobile communication integration, the corresponding communication topology diagram is constructed according to the corresponding formation method in different situations, in which each group is a node in the communication topology diagram; let d max Indicates the maximum reliable communication distance of one-hop communication between two nodes in the jungle. The default action mode is column exploration;

[0007] Step 2: Based on the propagation characteristics of electromagnetic waves in the jungle and the receiver sensitivity, the Tamir jungle path loss model is used to calculate the maximum reliable communication distance d between groups. max ; After networking, if the node exceeds the maximum reliable communication distance during movement, the communication device will alarm;

[0008] The d max The specific calculation process is as follows:

[0009] The horizontal straight-line distance between the transmitting and receiving antennas is recorded as d, the complex refractive index of vegetation is n, and L is set to represent the total path loss of radio waves from the transmitting antenna to the receiving antenna. The calculation formula is as follows:

[0010]

[0011]

[0012] L=L0+L s (dB)

[0013] Where L0 is the basic path loss of radio waves from the transmitting antenna to the receiving antenna without considering the ground, P t , P r Represent the transmit power and receive power of the signal, L s is the additional loss when both the transmitting and receiving antennas are inside the jungle and there is refraction of ground vegetation. λ0 is the vacuum wavelength. dB is the unit of sound. Im represents the imaginary part. lg represents the logarithm. s represents the sum of the difference between the top of the receiving antenna and the height of the jungle and the difference between the top of the transmitting antenna and the height of the jungle. s=2H-Z T -Z R , H represents the height of the jungle, Z T and Z R Respectively represent the height of the transmitting antenna and the height of the receiving antenna;

[0014] When the path loss L under the minimum signal-to-noise ratio requirement reaches the maximum, the corresponding horizontal straight-line distance between the transmitting and receiving antennas is the maximum reliable communication distance d max ;

[0015] Step 3: Using the one-hop interference model, the communication link interference graph is abstracted according to the communication topology graph. The specific contents are as follows:

[0016] For wireless communication in the jungle, due to the serious attenuation of radio waves, a one-hop interference model is used to abstract the communication link interference graph G according to the communication topology graph; each communication link in the communication topology graph is used as each node in the interference graph G, and two communication links that interfere with each other, i.e., nodes, are connected to form the interference graph G;

[0017] Step 4: The high-throughput and low-delay CSMA algorithm is constructed as an optimization problem with maximum throughput, and a distributed solution is performed to further improve the transmission delay performance of the data packet. The specific process is as follows:

[0018] The set of non-interference communication links is called an independent set; there are multiple independent non-interference communication links in each interference graph, and these independent non-interference communication links form an independent set. There are N different independent sets in all interference graphs G; X i ∈{0, 1} k represents the ith independent set, For X i The transmission state of communication link k in the communication link is: if communication link k is in the transmission state, its state is changed to an active link, that is, otherwise

[0019] The distributed access and transmission process of nodes is regarded as a distributed scheduling process for extracting a set of interference-free links, that is, the node sampling process in the interference graph, also known as the scheduling process of independent sets; then, the scheduling process of independent sets in the CSMA network is abstracted as a Markov process, called the Markov chain of independent set evolution; the state set of the Markov chain of independent set evolution is the state set of the interference-free communication link;

[0020] The state x in the Markov chain of independent set evolution i The stationary distribution probability p(x i ; r) is:

[0021]

[0022]

[0023] Where: The backoff factor set is the backoff vector r = (r1, r2, ..., r k ), C(r) represents the transmission state of all communication links in all independent sets contained in the interference graph G; i ; r) written as p i (r), r k is the backoff factor, K represents the total number of all communication links;

[0024] Assume that the average arrival rate of communication link k is λ k , calculated as follows:

[0025]

[0026] in is the steady-state probability corresponding to the packet arrival process, which is numerically equal to the number of packets arriving under communication link k divided by the number of packets arriving in the total time. and

[0027] Using the likelihood function F(r) to characterize the stationary distribution probability p(x i ; r) and the similarity between the steady-state probability of the target; the likelihood function F(r) is expressed as:

[0028]

[0029] When p i (r) and When they are equal, the likelihood function F(r) reaches its maximum, and the high-throughput and low-delay CSMA algorithm is constructed as an optimization problem with the maximum likelihood function:

[0030] sup r≥0 F(r)

[0031] Then, the distributed gradient descent method is used to solve the iterative process of the backoff factor approaching the optimal value, and the relationship between the iterative process of the backoff factor and the evolution process of the local packet queue length of the communication link k is analyzed. Then, the mapping relationship between the backoff factor and the local packet queue length is solved; according to the delay or packet queue length limit, the mapping relationship between the backoff factor and the local queue length is selected to achieve better delay performance.

[0032] In step 4, the queue length is compared with the threshold length. k Greater than or equal to the threshold captain Q max When , the delay performance is adjusted by changing the proportional relationship between the backoff factor and the length of the queue to the proportional relationship between the backoff factor and the exponential length of the queue e. The exponential relationship between the backoff factor and the length of the queue is shown in the following formula:

[0033]

[0034] Where t is the time, α is the constant step size, and the backoff factor r of the communication link k is k The adjustment period is b time units;

[0035] At this time, the backoff factor r k The value of 1 / exp(r k ) is smaller, and the backoff time follows the mean value of 1 / exp(r k ), so the average backoff time is small, the average access delay is low, and the communication effect is better;

[0036] When Captain Q k Less than the threshold captain Q max When , the proportional relationship between the backoff factor and the captain is as follows:

[0037] r k (t) = α / b·Q k (t)

[0038] At this time, the average backoff time of the communication link with a small queue is guaranteed to be longer, which reduces competition, prevents transmission collisions, and ensures the reliability of communication.

[0039] Beneficial effects of the present invention:

[0040] 1. The present invention fully considers the extreme environment of jungle where there is no base station, and realizes reliable communication by proposing an access method for communication networking.

[0041] 2. The high-throughput, low-latency distributed access and transmission algorithm based on CSMA involved in the present invention fully considers the impact of the length of the data packet queue on the delay, and improves the transmission delay of communication in a jungle environment by selecting the mapping relationship between the backoff factor and the queue length.

[0042] 3. This paper uses powerful mathematical theoretical tools, fully considers the propagation characteristics of electromagnetic waves in the jungle, and proposes an accurate Tamir jungle path loss model. By simulating the change of path loss in the jungle environment with the distance between the sending and receiving nodes by MATLAB, the maximum reliable communication distance d is obtained. max The solution method of

[0043] 4. It provides a basis for describing the communication topology of personnel performing different tasks in a jungle environment and arranging the number of teams according to the coverage area of ​​the action.

[0044] 5. The communication topology diagram and link interference diagram involved in the present invention are based on the Ad Hoc structure and the interference diagram respectively. The topology diagram describes the communication structure involved in different formations when implementing different tasks in the jungle; the interference diagram describes the interference relationship between communication links between different groups; it provides an important theoretical basis and technical reference for reliable communication in extreme environments such as the jungle. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings used in the description of the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the contents of the embodiments of the present invention and these drawings without paying any creative work.

[0046] Figure 1 It is a three-group-team search and rescue formation diagram;

[0047] Figure 2 The communication topology diagram of the three-group-team search and rescue formation;

[0048] Figure 3 It is a diagram of the capture formation of three groups and teams;

[0049] Figure 4 The communication topology diagram for the three-group-team capture formation;

[0050] Figure 5 It is a five-group-team search and rescue formation diagram;

[0051] Figure 6 The communication topology diagram of the five-group-team search and rescue formation;

[0052] Figure 7 A quick communication formation diagram for five groups and squads;

[0053] Figure 8 The communication topology diagram for the five-group-squad rapid communication formation;

[0054] Fig. 9 A diagram of the reinforcement formation for the five groups - squad leaders;

[0055] Fig.10 A communication topology diagram for the five-team leader reinforcement formation;

[0056] Fig.11 It is a five-group-team capture formation diagram;

[0057] Fig.12 The communication topology diagram for the five-group-team capture formation;

[0058] Fig.13 A formation diagram for five groups to defend against powerful enemies;

[0059] Fig.14 A communication topology diagram for five groups-squads to defend against strong enemy formations;

[0060] Fig.15 Explore the danger formation diagram for five groups - squads;

[0061] Fig.16 A communication topology map for five groups-teams exploring dangerous formations;

[0062] Fig.17 It is the total path loss diagram of Tamir model;

[0063] Fig.18 The communication link interference diagram for the three-group-team search and rescue formation;

[0064] Fig.19 For the three groups - the squad capture formation communication link interference map;

[0065] Fig. 20 The communication link interference diagram for the five-group-team search and rescue formation;

[0066] Fig.21 A communication link interference diagram for a five-group-squad rapid communication formation;

[0067] Fig. 22 Provide communication link interference diagram for the five-team leader reinforcement formation;

[0068] Fig.23 Capture the communication link interference map for the five groups - teams;

[0069] Fig.24 Provide five groups-squads with a communication link jammer to defend against strong enemy formations;

[0070] Fig.25 Explore dangerous formation communication link interference maps for five groups - teams;

[0071] Fig.26 The evolution of the length of the packet queue when the backoff factor is proportional to the length of the packet queue;

[0072] Fig. 27 This is the evolution of the captain under the mapping condition where the backoff factor is proportional to the e-exponential captain. DETAILED DESCRIPTION

[0073] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0074] Example 1

[0075] A self-organizing network method for jungle mobile communication, comprising the following contents:

[0076] The communication of this method is aimed at a squad formation; a squad contains x=3-5 groups, with a captain; a group contains 2-3 members, each of which has a member responsible for communication, who carries a communication device with a transceiver antenna (such as a wireless walkie-talkie); the distance between every two members in the group is controlled at 3-5 meters to ensure that they can support each other in time in case of emergencies;

[0077] In the present invention, a squad consisting of x groups is referred to as an "x-group-squad", for example, a squad consisting of five groups is referred to as a "five-group-squad"; one group corresponds to one node of the communication ad hoc network, and each group uses wireless communication to form an ad hoc network to maintain contact, ensure information transmission between groups, and the team leader issues command orders;

[0078] Step 1: Establish a connection relationship between communication nodes to form a communication topology graph;

[0079] According to the networking idea of ​​integrated mobile communication (taking into account the characteristics of the task and the communication performance of the self-organizing network), the corresponding communication topology diagram is constructed according to the formation method for different situations of typical tasks (listing tasks) such as jungle search and rescue and exploration. Each group is a node in the communication topology diagram; for the three groups-teams, the formation and its communication topology diagram are as follows Figure 1-4 As shown; for five groups-teams, the formation and its communication topology are as follows Figure 5-16 As shown. Let d max Indicates the maximum reliable communication distance of one-hop communication between two nodes in the jungle. The default action mode is column exploration. Explain in detail the communication topology structure corresponding to the formation under each task situation, and describe the communication distance between group nodes.

[0080] Step 2: Based on the propagation characteristics of electromagnetic waves in the jungle and the receiver sensitivity, the Tamir jungle path loss model is used to calculate the maximum reliable communication distance d between groups.max After networking, if the node moves beyond the maximum reliable communication distance during the movement, the communication device (such as a wireless walkie-talkie) will give an alarm prompt to尽量 avoid losing contact.

[0081] The propagation characteristics of electromagnetic waves are as follows: When electromagnetic waves propagate in the jungle environment, the propagation environment is divided into four major regions according to different propagation media, namely: the ground layer, the vegetation layer, the atmosphere (including the troposphere) and the ionosphere. When both the transmitting and receiving antennas are inside the vegetation layer, there are four basic propagation modes: the lateral wave mode, the knife-edge diffraction mode, the sky wave mode and the hybrid mode. Experiments show that when the radio wave frequency f <= 15MHz and the horizontal straight-line distance d >= 10Km between the transmitting and receiving antennas, the sky wave mode is dominant; when 15MHz < f < 400MHz and 400m < d < 10Km, the influence of the sky wave mode is small and the lateral wave mode is dominant.

[0082] The research idea of the theoretical analysis model of jungle path loss is mainly to layer the propagation environment according to the medium situation, and then consider the propagation modes of radio waves in different layers, and deduce the path loss and additional loss of radio waves based on Maxwell's equations.

[0083] This method uses the classical model in jungle electromagnetic wave propagation prediction - the Tamir jungle path loss model, where d max The specific calculation process is as follows:

[0084] The horizontal straight-line distance between the transmitting and receiving antennas is denoted as d, and the complex refractive index of the vegetation is n, where n 2 = ε1 - j(σ1 / wε0) = ε1 - j60σ1λ0, where δ1 represents the average relative permittivity of the vegetation layer, w represents the frequency of the transmitted signal, j represents the complex number symbol, w represents the frequency of the transmitted signal, σ1 represents the average conductivity of the vegetation medium, and δ0 is the absolute permittivity; and ε1 ≈ 1, 60σ1λ0 << 1, so the complex refractive index n of the vegetation is close to 1; Let L represent the total path loss of the radio wave from the transmitting antenna to the receiving antenna, and its calculation formula is as follows:

[0085]

[0086]

[0087] L = L0 + L s (dB) (3)

[0088] Among them, L0 is the basic path loss of the radio wave from the transmitting antenna to the receiving antenna without considering the ground, P t 、P r respectively represent the transmission power and reception power of the signal, L sis the additional loss when both the transmitting and receiving antennas are inside the jungle and there is refraction of ground vegetation. λ0 is the vacuum wavelength. dB is the unit of sound. Im represents the imaginary part. lg represents the logarithm. s represents the sum of the difference between the top of the receiving antenna and the height of the jungle and the difference between the top of the transmitting antenna and the height of the jungle. s=2H-Z T -Z R , H represents the height of the jungle (measured on site), Z T and Z R Respectively represent the height of the transmitting antenna and the height of the receiving antenna;

[0089] When the path loss L under the minimum signal-to-noise ratio requirement reaches the maximum, the corresponding horizontal straight-line distance between the transmitting and receiving antennas is the maximum reliable communication distance d max ;

[0090] Step 3: Using the one-hop interference model, the communication link interference graph is abstracted according to the communication topology graph. The specific contents are as follows:

[0091] For wireless communication in the jungle, due to the serious attenuation of radio waves, a one-hop interference model is used to abstract the communication link interference graph G according to the communication topology graph; each communication link in the communication topology graph is used as each node in the interference graph G, and two communication links that interfere with each other, i.e., nodes, are connected to form the interference graph G; that is, if two communication links interfere with each other, then there will be an edge between the corresponding two nodes in the interference graph G; otherwise, there will be no edge; the communication link interference graphs corresponding to the communication topology graphs of the three and five teams are as follows: Figure 18-25 As shown, the subsequent specific implementation manner will describe in detail the interference relationship between the communication links in the interference graph.

[0092] Step 4: Study the distributed access and transmission method with high throughput and low latency based on CSMA.

[0093] The high-throughput and low-delay CSMA algorithm is constructed as an optimization problem with maximum throughput, which is solved in a distributed manner and the transmission delay performance of data packets is further improved. The specific process is as follows:

[0094] The set of non-interference communication links is called an independent set; there are multiple independent non-interference communication links in each interference graph, and these independent non-interference communication links form an independent set. There are N different independent sets in all interference graphs G (non-interference links are independent, and their set is an independent set, where all independent non-interference communication links in each interference graph form an independent set); X i ∈{0, 1} k represents the ith independent set, For X iThe transmission state of communication link k in the communication link is: if communication link k is in the transmission state, its state is changed to an active link, that is, otherwise That is to say The value is 1 when transmitting, and 0 when not transmitting.

[0095] The distributed access and transmission process of nodes is regarded as a distributed scheduling process for extracting a set of interference-free links, that is, a node sampling process in the interference graph, also known as an independent set scheduling process; then, the scheduling process of independent sets in the CSMA network (the communication network corresponding to the interference graph) is abstracted as a Markov process, called an independent set evolution Markov chain; the state set of the independent set evolution Markov chain is the state set of the interference-free communication link (that is, whether the link is transmitting), that is, the independent set X after the transmission state of the communication link is assigned i ;

[0096] The state x in the Markov chain of independent set evolution i The stationary distribution probability p(x i ; r) is:

[0097]

[0098]

[0099] The above sum Covering all feasible states, that is, independent sets, that is, the transmission states of all communication links in all independent sets, that is, the transmission states of all transmission links without interference, the backoff factor set, that is, the backoff vector r = (r1, r2, ..., r k ), C(r) represents the transmission state of all communication links in all independent sets contained in the interference graph G; i ; r) written as p i (r), r k It is defined as the backoff factor, K represents the total number of all communication links in the network;

[0100] In carrier sensing, when there are data packets waiting to be transmitted in the node's cache, the node first senses the wireless channel. If there is an interfering link transmitting data, the node will wait for a random period of time, which is called the backoff time, and it follows the mean value of 1 / exp(r k ) is an exponential distribution. After the backoff ends, the node performs carrier sensing again. If the channel is idle (i.e., there is no interference link transmission), the sending node of link k starts transmitting. It can be seen that the backoff factor r k The larger the value, the shorter the average backoff time and the lower the access delay.

[0101] The Markov chain of independent set evolution is time reversible, and the average service rate of link k is equal to the sum of the stationary distribution probabilities of the independent set that link k is an active link; therefore, the average service rate of communication link k is s k (r)(r is the independent variable, s k As a function, the terminal's service rate for data packets (the number of service data packets per unit time) is calculated as follows:

[0102]

[0103] Assume that the average arrival rate of communication link k (the number of data packets arriving at the terminal per unit time) is λ k , and the arrival rate vector is expressed as Average arrival rate λ k Calculate as follows:

[0104]

[0105] in is the steady-state probability corresponding to the packet arrival process, which is numerically equal to the number of packets arriving under communication link k divided by the number of packets arriving in the total time. and Let C represent the set of strictly feasible λ, which represents a set that satisfies the set of positive real numbers λ, where λ is a convex combination of independent sets, so that the service rate converges to the arrival rate. In actual networks, the throughput (throughput is the number of packets transmitted per unit time) is maximum when the cache is empty. At this time, the actual average service rate is equal to the average arrival rate. Formula (6) can be used to map the average arrival rate of each link to the target steady-state probability of the Markov chain evolved by the independent set. Based on the idea of ​​Markov Monte Carlo, the stationary distribution probability p of the Markov chain evolved by the independent set can be controlled by controlling the backoff factor. i (r) Steady-state probability of moving toward the target Approaching, thus achieving maximum throughput; by making state x i The stationary distribution probability of approaches the steady-state probability of arriving packets so that the average service rate is equal to the average arrival rate.

[0106] In view of this, the likelihood function F(r) is used to characterize the stationary distribution probability p(x i ; r) and the similarity between the steady-state probability of the target; the likelihood function F(r) is expressed as:

[0107]

[0108] The stationary distribution probability p of the state in the CSMA Markov chain iSubstituting the expression of (r) into (7), we can obtain the second equation in (7). When p i (r) and When they are equal, the likelihood function F(r) reaches its maximum, and the high-throughput and low-delay CSMA algorithm is constructed as an optimization problem with the maximum likelihood function:

[0109] sup r≥0 F(r) (8)

[0110] Then, the distributed gradient descent method is used to solve the iterative process of the backoff factor approaching the optimal value, and the relationship between the iterative process of the backoff factor and the evolution process of the local packet queue length of the communication link k (the sending node) is analyzed. Then, the mapping relationship between the backoff factor and the local packet queue length is solved; through simulation comparison, the difference in delay performance under different mapping relationships is found; finally, according to the delay or packet queue length limit, the mapping relationship between the backoff factor and the local queue length is selected to achieve better delay performance.

[0111] In step 4, the queue length is compared with the threshold length. k Greater than or equal to the threshold captain Q max When , the delay performance is adjusted by changing the proportional relationship between the backoff factor and the length of the queue to the proportional relationship between the backoff factor and the exponential length of the queue e. The exponential relationship between the backoff factor and the length of the queue is shown in the following formula:

[0112]

[0113] Where t is the time, α is a small constant step size, and the backoff factor r of the communication link k is k The adjustment period is b time units;

[0114] At this time, the backoff factor r k The value of 1 / exp(r k ) is smaller, and the backoff time follows the mean value of 1 / exp(r k ), so the average backoff time is small, the average access delay is low, and the communication effect is better;

[0115] When Captain Q k Less than the threshold captain Q max When , the proportional relationship between the backoff factor and the captain is as follows:

[0116] r k (t) = α / b·Q k (t)

[0117] At this time, the average backoff time of the communication link with a small queue is guaranteed to be longer, which reduces competition, prevents transmission collisions, and ensures the reliability of communication.

[0118] Example 2

[0119] A self-organizing network method for mobile communication in jungle, comprising the following contents:

[0120] Step 1: According to the characteristics of the required formation, establish the connection relationship between communication nodes, that is, form a communication topology diagram, as shown in the following figure: Figure 1-Figure 16 In the figure, each node represents a group, and the dotted line represents the distance d between nodes. max The dotted circle represents the detection range, and the double-headed arrow represents the maximum distance d between the groups. max reliable communication.

[0121] Group Three - Team:

[0122] When the team conducts a search and rescue operation in the jungle: the formation of the three teams is an equilateral triangle. Figure 1 , with a side length of d max At this time, the coverage area is the largest, the search and rescue range is the widest, and it is most suitable for search and rescue operations. Its communication topology is as follows Figure 2 As shown, the three teams can communicate with each other. There are three possible communication paths between the nodes of the three groups, such as (1,2), (1,3), and (2,3). The communication distance between them is one hop d. max .

[0123] When the team is carrying out a capture operation in the jungle: the team leader is in the middle, and the other two teams are at a distance d in front and behind them. max The location of Figure 3 This formation is convenient for the protection team leader to issue orders, and it is convenient for the middle team to provide support when the front and rear teams are attacked, which is suitable for arrest. Figure 4 As shown in the figure, the communication distance between (1,2) and (2,3) is one hop, and the communication distance between (1,3) needs to pass through node 2, which requires a two-hop communication distance.

[0124] Group 5 - Team:

[0125] When the team conducts a search and rescue operation in the jungle: the formation of the five teams is a regular pentagon. Figure 5 , with a side length of d max At this time, the coverage area is the largest, the search and rescue range is the widest, and it is most suitable for search and rescue operations. Its communication topology is as follows Figure 6 As shown, the number of nodes in each group is There are possibilities, such as (1,2), (1,5), (2,3), (3,4), (4,5) The communication between these nodes only needs one hop, which saves time and is highly efficient, while (1,4), (1,3), (2,4), (2,5), (3,5) The fastest communication between these nodes is two hops.max Reliable transmission.

[0126] When the team conducts flexible coordinated operations in the jungle: the formation of the five teams is as follows: Figure 7 This formation facilitates rapid communication between groups and can enhance the efficient collaboration between teams during operations, making it suitable for flexible and coordinated operations in the jungle.

[0127] Its communication topology is as follows: Figure 8 The shortest communication distance between every two nodes is one or two hops. The communication combinations are (1,2), (2,3), (1,4), (2,4), (2,5), (3,5), (4,5). The communication distance between these groups is one hop, and the communication distance between these groups is two hops.

[0128] When the group is deep in the enemy's heart: the formation of the five groups of teams is as follows Fig. 9 When group node 5 is the leader, the distance between the other four group nodes and the leader group node is d max The communication distance between the captain and other teams is one hop, which is convenient for command and quick support. This formation is suitable for the adverse situation when the team is surrounded by the enemy. Fig.10 As shown, the communication distance between nodes (1,5), (2,5), (3,5), and (4,5) is one hop, and the communication between (1,2), (2,3), (3,4), (1,4), (2,4), and (1,3) needs to go through the team leader node 5, with a communication distance of two hops.

[0129] When the team carried out the arrest operation: Fig.11 The formation shown is suitable for capture operations. There are three different combat plans according to the position of the captain. The communication topology is as follows: Fig.12 .

[0130] The first type: The captain is at node 1. In this case, the captain is the first to lead the team, which is convenient for capturing the enemy and protecting his team members at the same time. (1,2) The communication distance between nodes is one hop, and the communication distance between node 1 and other nodes is greater than one hop, which is not convenient for information exchange.

[0131] The second type: The captain is at node 3. In this case, it is convenient for the captain to issue orders to the rest of the team and also to reinforce teammates in time. The communication distance between nodes (3,4), (3,2), and (3,5) is one hop, which is convenient for the captain to exchange information with other team members and facilitate command.

[0132] The third type: The captain is at node 4 or 5. In this case, the captain is at the rear of the team. While capturing, he can prevent the enemy from attacking the rear and facilitate the escort of the wounded. In this case, the communication distance between the captain's node and node 3 is one hop, and the communication distance with other nodes is farther, all greater than one hop.

[0133] When the group is defending against a strong enemy: the formation of the five teams is as follows: Fig.13 As shown in the figure, the captain is located at node 1, nodes 4 and 5 are the vanguard group, nodes 2 and 3 provide reinforcements and exchange information with the captain to report the situation of the vanguard group. This formation is suitable for resisting strong enemies and protecting the captain's command. Its communication topology is as follows Fig.14 As shown, the communication distance between nodes (1,2), (1,3), (2,3), (2,4), (4,5), and (3,5) is one hop. The communication distance between nodes (1,4) and (1,5) is two hops, which requires information to be transmitted through nodes 2 and 3. The communication distance between nodes (3,4) and (2,5) is also two hops.

[0134] When the group was about to go deep into the jungle to explore the danger: the formation of the five teams was as follows: Fig.15 When the captain is at node 1, he needs to lead the way, followed by the group at node 2 and the group at node 3, and finally nodes 4 and 5. This formation enters the jungle in batches, and the captain is the pioneer, which is suitable for actions against the enemy and exploring the dangers in the jungle, which can protect teammates and reduce casualties. The communication topology is as follows: Fig.16 As shown in Figure 2, the communication distance between nodes (1,2), (1,3), (2,3), (2,4), (4,5), and (3,5) is one hop. The communication distance between nodes (1,4) and (1,5) is two hops, which means that information needs to be transmitted through nodes 2 and 3. The communication distance between nodes (3,4) and (2,5) is also two hops. Fig.14 The communication topology is the same.

[0135] Step 2: Based on the propagation characteristics of electromagnetic waves in the jungle and the receiver sensitivity, the maximum reliable communication distance d between groups is calculated using the Tamir jungle path loss model. max ; After networking, if the node exceeds the maximum reliable communication distance during movement, the device will alarm to avoid loss of connection as much as possible; the details are as follows:

[0136] We simulated the path loss in a jungle environment as it changes with the distance between the sending and receiving nodes. Fig.17 The total path loss results of Tamir's model are shown when the jungle height is 25 meters, the transmitting antenna height is 16 meters, and the receiving antenna height is 5 meters.

[0137] d max The value of:

[0138] d max is the maximum reliable communication distance, the signal-to-noise ratio between group nodes is defined as γ, and the minimum signal-to-noise ratio requirement is defined as SNR min , the maximum transmission power of the communication device is defined as P max , whose noise power is N 噪声 , the receiving power of the signal at the receiving end (communication equipment) is S 接收 , the path loss in the jungle environment is L 路径损耗 .

[0139] The calculation process is as follows:

[0140]

[0141] γ ≥ SNR min (10)

[0142] S 接收 =P max -L 路径损耗 (11)

[0143] From formula (9) and formula (10), we can know that: according to the minimum signal-to-noise ratio requirement SNR between group nodes (nodes correspond to different groups within a team, because each group has a member responsible for communication, they carry communication equipment similar to transceiver antennas, so the communication between groups has signal-to-noise ratio requirements) min , and the noise power N in the communication equipment 噪声 , we can get the received power S 接收 , then according to formula (11) and the maximum transmission power P of the communication device max , we can get the maximum path loss L 路径损耗 , and finally through Fig.17 The path loss in the jungle environment under the Tamir model shown in the figure varies with the distance between the sending and receiving nodes, corresponding to the maximum reliable communication distance d between the sending and receiving nodes. max ; If the distance exceeds this value, communication will not be possible according to the original topology; if the device cannot communicate with any other group, the device will alarm to avoid loss of connection as much as possible.

[0144] Also using d max The area covered by the squads, i.e. the area surrounded by the squads, under the above three-group squad and five-group squad formations was calculated. The calculation method is as follows:

[0145]

[0146]

[0147] When the total area that needs to be covered is known, calculate the number of squads that need to be sent by dividing the total area by the area of ​​the squads in different situations in the above table.

[0148] Step 3: Using the one-hop interference model, based on the communication topology, abstract the communication link interference graph and draw the communication link interference graph corresponding to the communication topology. Figure 18-25 As shown. The lines between the links in the interference graph represent the interference relationship between the two links. There is an interference relationship between the communication links with a distance of one hop connected to the same node, but there is no interference relationship between the communication links with a distance greater than one hop. The following describes the interference graphs corresponding to different formations in detail:

[0149] The communication link interference diagram of the three-group search and rescue formation: the communication link between node 1 and node 2 is defined as L1; the communication link between node 1 and node 3 is defined as L2; ​​the communication link between node 2 and node 3 is defined as L3, the interference diagram is as follows Fig.18 .

[0150] Three-group-squad capture formation communication link interference graph: The communication link between node 1 and node 2 is defined as L1; the communication link between node 2 and node 3 is defined as L2, the interference graph is as follows Fig.19 .

[0151] Five-group-team search and rescue formation communication link interference graph: the communication link between node 1 and node 2 is defined as L1; the communication link between node 2 and node 3 is defined as L2; ​​the communication link between node 3 and node 4 is defined as L3; the communication link between node 4 and node 5 is defined as L4; the communication link between node 1 and node 5 is defined as L5. The interference graph is as follows Fig. 20 .

[0152] Five-group-squad rapid communication formation communication link interference graph: define the communication link between node 1 and node 2 as link L1; define the communication link between node 2 and node 3 as L2; ​​define the communication link between node 2 and node 4 as L3; define the communication link between node 2 and node 5 as L4; define the communication link between node 1 and node 4 as L5; define the communication link between node 4 and node 5 as L6; define the communication link between node 3 and node 5 as L7. The interference graph is shown in the figure. Fig.21 .

[0153] Communication link interference diagram of group 5 - team leader reinforcement formation: define the communication link between node 1 and node 5 as L1; define the communication link between node 2 and node 5 as L2; ​​define the communication link between node 3 and node 5 as L3; define the communication link between node 4 and node 5 as L4. The interference diagram is as follows: Fig. 22 .

[0154] Five groups - team capture pairs of communication link interference graphs: define the communication link between node 1 and node 2 as L1; define the communication link between node 2 and node 3 as L2; ​​define the communication link between node 3 and node 4 as L3; define the communication link between node 3 and node 5 as L4. The interference graph is as follows: Fig.23 .

[0155] Communication link interference diagram of five groups - teams resisting strong enemy formations: define the communication link between node 1 and node 2 as L1; define the communication link between node 1 and node 3 as L2; ​​define the communication link between node 2 and node 3 as L3; define the communication link between node 2 and node 4 as L4; define the communication link between node 4 and node 5 as L5; define the communication link between node 3 and node 5 as L6. The interference diagram is as follows Fig.24 .

[0156] Five groups - team exploration dangerous formation communication link interference diagram: define the communication link between node 1 and node 2 as L1; define the communication link between node 1 and node 3 as L2; ​​define the communication link between node 2 and node 3 as L3; define the communication link between node 2 and node 4 as L4; define the communication link between node 4 and node 5 as L5; define the communication link between node 3 and node 5 as L6, the interference diagram is as follows Fig.25 .

[0157] Step 4: Construct the Lagrangian function corresponding to the optimization problem (8). Then, we get the extreme value condition for the optimal throughput. Using formula (5), after sorting, it is as follows:

[0158]

[0159] Using the gradient algorithm in convex optimization to solve formula (8), we can get the backoff factor r k The iterative process (13).

[0160] r k (t+1)=[r k (t)+α·(λ′ k (t)-s′ k (t))] (13)

[0161] where α is a small constant step size.

[0162] Assume that the backoff factor r of communication link k is k The adjustment period is b time units; so the cycle count increases by 1 every b time units; for the convenience of analysis, at the communication link k, it is assumed that the data packets arriving between time t-1 and t are stored in a temporary buffer and added to the data packet queue at time t. Let λ′ k(t) is the average arrival rate between time t-1 and t, let s′ k (t) is the average service rate between time t and t+1. Then the length of the packet queue Q at link k is k The evolution process of (the queue length at the transmitting node of link k) is:

[0163] Q k (t+1)=[Q k (t)+b·(λ′ k (t)-s k (t))] + (14)

[0164] Comparing (13) and (14), we can obtain the proportional relationship between the backoff factor and the length of the packet queue (15):

[0165] r k (t) = α / b·Q k (t) (15)

[0166] The delay performance is adjusted by changing the proportional relationship between the backoff factor and the length of the queue to the proportional relationship between the backoff factor and the length of the e-exponential queue:

[0167]

[0168] From the above proportional relationship, we know that when the backoff factor is stable, the queue length of the data packet is also stable, which means that the service rate of the arriving data packet converges to the arrival rate, which is also the extreme condition for the optimal throughput. The evolution of the queue length under different mappings of the backoff factor and the queue length is simulated to analyze whether the throughput can achieve the optimal solution and the stability of the delay, such as Figure 26-27 The analysis is as follows:

[0169] Fig.26 The evolution of the queue length when the backoff factor is proportional to the queue length. It can be seen from the figure that although the queue length has some fluctuations, they are still stable. The stability of the queue length means that the service rate can converge to the arrival rate, that is, the throughput can reach the maximum. At the same time, the stability of the queue length means that the delay is stable.

[0170] Fig. 27 The evolution of the captain in the case of a mapping where the backoff factor is proportional to the e-exponential captain. The captain is still stable, and the fluctuation range of the captain value is reduced, and the delay is small.

[0171] In order to achieve a balance between latency performance and reliability, the threshold length is set to Q max , when Captain Q k Greater than or equal to the threshold captain Q maxWhen , the exponential relationship between the backoff factor and the length is selected, as shown in formula (16). At this time, the backoff factor r k The value of is large, and the backoff time follows the mean value of 1 / exp(r k ), so the average backoff time is small and the average access delay is low. k Less than the threshold captain Q max When , the proportional relationship between the backoff factor and the length of the link is selected, as shown in formula (15). In this case, the average backoff time of the link with a small length can be guaranteed to be longer, which can reduce competition, prevent transmission collisions, and ensure the reliability of communication.

[0172] In summary, the method proposed in this paper can provide a theoretical basis and technical reference for realizing efficient mobile communication in a series of actions in an extreme environment such as the jungle where there is no base station. Specifically, it mainly includes drawing corresponding communication topology diagrams according to the formations corresponding to different situations; calculating the maximum reliable communication distance d between groups max ; Design the link interference graph corresponding to the communication topology; According to the relationship between the queue length of the data packet and the threshold length, select the value of the backoff factor to achieve a balance between delay performance and reliability.

[0173] (1) Using step 1) of the present invention: when personnel perform different action tasks in the jungle, draw communication topology diagrams corresponding to different formations to help the troops understand the coverage of their reliable communication and the communication status between group nodes during the action, thus providing a theoretical basis for personnel to act in the jungle.

[0174] (2) Using step 2 of the present invention: establishing the Tamir model, and deriving a solution to the maximum reliable communication distance by simulating the change of path loss with the distance between the transmitting and receiving nodes in a jungle environment. max , helping troops plan the distance between teams when operating in the jungle; when the area that personnel need to cover is known, the number of teams that need to be dispatched can be calculated by using the area of ​​the teams in different formations of three groups-teams and five groups-teams. This provides data reference for personnel operations in the jungle.

[0175] (3) Apply step 3 of the present invention: use the one-hop interference model to abstract the communication link interference graph according to the communication topology graph, and draw the communication link interference graph corresponding to the communication topology graph. This helps personnel intuitively understand the interference relationship between group nodes in different formations, and provides a theoretical basis for personnel to achieve efficient mobile communication when operating in the jungle.

[0176] (4) Using step 4 of the present invention: we can compare the queue length of the data packet with the threshold length Q maxThe size relationship between the length of the queue and the length of the backoff factor is selected to achieve a balance between latency performance and reliability: when the queue length is greater than or equal to the threshold queue length Q max When , we choose the backoff factor to be proportional to the length of the exponential length e. In this case, the backoff factor r k The larger the value, the smaller the average backoff time and the lower the average access delay. max When selecting the backoff factor in direct proportion to the length of the link, the average backoff time of the link with a smaller length can be guaranteed to be longer, which can reduce competition, prevent transmission collisions, and ensure the reliability of communication. This provides an important theoretical basis and technical reference for personnel to achieve low-latency and high-reliability communication when operating in extreme environments such as jungles.

[0177] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the protection scope of the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention. These simple variations all belong to the protection scope of the present invention.

[0178] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0179] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A self-organizing network method for jungle mobile communication, characterized in that It includes the following: Step 1: Establish a connection relationship between communication nodes to form a communication topology graph; According to the networking concept of mobile communication integration, corresponding communication topology diagrams are constructed for different situations and corresponding formation methods, in which each group is a node in the communication topology diagram; Let d max Indicates the maximum reliable communication distance for one-hop communication between two nodes in the jungle. The default action mode is column exploration; Step 2: Based on the propagation characteristics of electromagnetic waves in the jungle and the receiver sensitivity, the Tamir jungle path loss model is used to calculate the maximum reliable communication distance d between groups. max ; After networking, if the node exceeds the maximum reliable communication distance during movement, the communication device will alarm; The d max The specific calculation process is as follows: The horizontal straight-line distance between the transmitting and receiving antennas is d, the complex refractive index of vegetation is n, and L is the total path loss of radio waves from the transmitting antenna to the receiving antenna. The calculation formula is as follows: L=L0+L s (dB) Where L0 is the basic path loss of radio waves from the transmitting antenna to the receiving antenna without considering the ground, P t , P r Represent the transmit power and receive power of the signal, L s is the additional loss when both the transmitting and receiving antennas are inside the jungle and there is refraction of ground vegetation. λ0 is the vacuum wavelength. dB is the unit of sound. Im represents the imaginary part. lg represents the logarithm. s represents the sum of the difference between the top of the receiving antenna and the height of the jungle and the difference between the top of the transmitting antenna and the height of the jungle. s=2H-Z T -Z R , H represents the height of the jungle, Z T and Z R Respectively represent the height of the transmitting antenna and the height of the receiving antenna; When the path loss L under the minimum signal-to-noise ratio requirement reaches the maximum, the corresponding horizontal straight-line distance between the transmitting and receiving antennas is the maximum reliable communication distance d max ; Step 3: Using the one-hop interference model, the communication link interference graph is abstracted according to the communication topology graph. The specific contents are as follows: For wireless communication in the jungle, due to the serious attenuation of radio waves, a one-hop interference model is used to abstract the communication link interference graph G according to the communication topology graph; each communication link in the communication topology graph is used as each node in the interference graph G, and two communication links that interfere with each other, i.e., nodes, are connected to form the interference graph G; Step 4: The high-throughput and low-delay CSMA algorithm is constructed as an optimization problem with maximum throughput, and a distributed solution is performed to further improve the transmission delay performance of the data packet. The specific process is as follows: The set of non-interference communication links is called an independent set; there are multiple independent non-interference communication links in each interference graph, and these independent non-interference communication links form an independent set. There are N different independent sets in all interference graphs G; X i ∈{0, 1} k represents the ith independent set, For X i The transmission state of communication link k in the communication link is: if communication link k is in the transmission state, its state is changed to an active link, that is, otherwise The distributed access and transmission process of nodes is regarded as a distributed scheduling process for extracting a set of interference-free links, that is, the node sampling process in the interference graph, also known as the scheduling process of independent sets; then, the scheduling process of independent sets in the CSMA network is abstracted as a Markov process, called the Markov chain of independent set evolution; the state set of the Markov chain of independent set evolution is the state set of the interference-free communication link; The state x in the Markov chain of independent set evolution i The stationary distribution probability p(x i ; r) is: Where: The backoff factor set is the backoff vector r = (r1, r2, ..., r k ), C(r) represents the transmission state of all communication links in all independent sets contained in the interference graph G; i ; r) written as p i (r), r k is the backoff factor, K represents the total number of all communication links; Assume that the average arrival rate of communication link k is λ k , calculated as follows: in: is the steady-state probability corresponding to the packet arrival process, which is numerically equal to the number of packets arriving under communication link k divided by the number of packets arriving in the total time. and Using the likelihood function F(r) to characterize the stationary distribution probability p(x i ; r) and the similarity between the steady-state probability of the target; the likelihood function F(r) is expressed as: When p i (r) and When they are equal, the likelihood function F(r) reaches its maximum, and the high-throughput and low-delay CSMA algorithm is constructed as an optimization problem with the maximum likelihood function: sup r≥0 F(r) Then, the distributed gradient descent method is used to solve the iterative process of the backoff factor approaching the optimal value, and the relationship between the iterative process of the backoff factor and the evolution process of the local packet queue length of the communication link k is analyzed. Then, the mapping relationship between the backoff factor and the local packet queue length is solved; according to the delay or packet queue length limit, the mapping relationship between the backoff factor and the local queue length is selected to achieve better delay performance.

2. A self-organizing network method for jungle mobile communication according to claim 1, characterized in that In step 4, the queue length is compared with the threshold length. k Greater than or equal to the threshold captain Q max When , the delay performance is adjusted by changing the proportional relationship between the backoff factor and the length of the queue to the proportional relationship between the backoff factor and the exponential length of the queue e. The exponential relationship between the backoff factor and the length of the queue is shown in the following formula: Where t is the time, α is the constant step size, and the backoff factor r of the communication link k is k The adjustment period is b time units; At this time, the backoff factor r k The value of 1 / exp(r k ) is smaller, and the backoff time follows the mean value of 1 / exp(r k ), so the average backoff time is small, the average access delay is low, and the communication effect is better; When Captain Q k Less than the threshold captain Q max When , the proportional relationship between the backoff factor and the captain is as follows: r k (t)=α / b·Q k (t) At this time, the average backoff time of the communication link with a small queue is guaranteed to be longer, which reduces competition, prevents transmission collisions, and ensures the reliability of communication.

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