CN107071817A - A kind of mobile sensor network chance retransmission method towards fire rescue scene - Google Patents

Abstract

The invention belongs to the technical field of mobile sensor network opportunistic forwarding, and discloses a mobile sensor network opportunistic forwarding method for fire rescue scenarios, which specifically includes the following steps: S1: calculating node stability values; S11: calculating nodes of small-scale moving sensor nodes Stability value; S12: Calculate the node stability value of nodes composed of firefighters; S13: Calculate the node stability value of sensor nodes moving in a large range; S2: Calculate the proportional relationship between nodes; S3: Formulate a forwarding strategy based on stability. The present invention takes into account the dynamics and complexity of the fire rescue scene, and makes full use of the initiative of firefighter nodes to forward messages purposefully. Under different network scales, the present invention can achieve a higher delivery rate. Moreover, the present invention has relatively small network overhead and is suitable for fire rescue scenarios.

Description

An Opportunistic Forwarding Method for Mobile Sensor Networks in Fire and Rescue Scenarios

technical field

The invention belongs to the technical field of opportunistic forwarding of a mobile sensor network, and in particular relates to a method for opportunistic forwarding of a mobile sensor network facing a fire rescue scene.

Background technique

Mobile sensor networks (Wireless Sensor Networks, WSNs) are multi-hop self-organizing networks composed of a large number of small, low-cost sensor nodes communicating with each other. Because of its rapid deployment, strong invulnerability, real-time and other characteristics, it has more and more extensive application prospects. In the network, the communication links between nodes exist with a certain probability, relying on the communication opportunities brought by node movement to realize data forwarding, but at the same time there may not be a communication path from the sensor node to the destination node, so in the network Nodes rely on the "carry-store-forward" method to forward messages over multiple hops to form an independent self-organizing network. Based on the particularity of mobile sensor networks, it is suitable for scenarios where basic network facilities cannot be laid in advance and rapid automatic networking is required.

The traditional routing algorithm is mainly carried out along two basic strategies: the routing algorithm based on redundancy spreads the message to the network through copying, and forms a routing strategy for multi-message storage. Another routing algorithm based on utility value provides reference for node forwarding data through calculation of utility value, and screens one or more forwarding nodes. This type of prediction algorithm is suitable for scenarios where nodes move regularly. In addition, some scholars set up a special scene in which moving paths, patrol cars, personnel, etc. are damaged to varying degrees by natural disasters, compared the performance of traditional algorithms in ordinary and special scenes, and pointed out that the traditional In special scenarios, all routing indicators of the routing algorithm are degraded, and cannot be fully applied to special scenarios. At present, there are mainly two research points on opportunistic networks in special scenarios: mobility models and routing algorithms. One is to reflect the movement properties of nodes by establishing a movement model suitable for special scenes, and obtain the contact rules of nodes in special scenes through analysis. This kind of research is mainly based on the social nature of people, which is not suitable for fire rescue scenes where there is no movement law. The second is to start with the routing algorithm itself. The research on the algorithm is mainly to improve the success rate of message transmission and reduce the delay of message forwarding. These hypotheses all have a premise. The main object in the scene is a person who moves with certain regularity, which is obviously not applicable to the fire rescue scene with most irregular nodes.

The fire rescue scenario is one of the important application scenarios of the mobile sensor network. After a fire or other disaster occurs, the basic communication facilities are damaged or unavailable. In order to rescue and rescue disasters, it is necessary to quickly obtain information from various regions. At this time, individuals in the fire or mobile sensor nodes are needed to quickly deploy the network. The independent networking capability and self-organization characteristics of the mobile sensor network are a good choice for communication in fire rescue scenarios. But in the fire rescue scene, there are a large number of irregularly moving nodes. As nodes join and exit, the links between nodes will change and the network topology will change in real time. Therefore, there is no complete path in the network, and how to transmit messages on a dynamic path is the most important issue.

Contents of the invention

The purpose of the present invention is to solve the above-mentioned shortcomings in the prior art, and propose a mobile sensor network opportunistic forwarding method for fire rescue scenarios.

For this reason, the technical solution proposed by the present invention is a mobile sensor network opportunistic forwarding method for fire rescue scenarios, which specifically includes the following steps:

S1: Calculate node stability value;

S11: Calculate the node stability value of the sensor node moving in a small range;

S12: Calculate the node stability value of the nodes composed of firefighters;

S13: Calculate the node stability value of the sensor node moving in a large range;

S2: Calculate the proportional relationship between nodes;

S3: Formulate a stability-based forwarding strategy.

Further, the above step S1 specifically includes the following steps:

a. Calculate the distance change value between nodes from time t to time t+1;

b. Select the minimum value of the distance change between the node and the neighbor node, and then calculate the variance of the distance change;

c. Normalize the variance to , and calculate the stability factor at time t;

d. According to the size of the node stability value, the nodes are divided into small-range mobile nodes, large-scale mobile nodes, and firefighter nodes.

Further, the above step S2 specifically includes the following steps:

a. Estimate the delivery rate of small-scale mobile nodes, large-scale mobile nodes, and firefighter nodes;

b. Calculate the proportional relationship between nodes by the delivery rate;

c. Calculate the number of three types of nodes, among which the number of firefighter nodes is fixed.

Further, the above step S3 specifically includes the following steps:

a. When communicating, use the active mobility of the firefighter node to forward messages;

b. In extreme cases, use a large range of mobile nodes for message forwarding.

Compared with prior art, the beneficial effect of the present invention is:

1. The present invention takes into account the dynamics and complexity of fire rescue scenarios, and makes full use of the initiative of firefighter nodes to forward messages purposefully.

2. Under different network scales, the present invention can achieve a higher delivery rate.

3. The present invention has relatively small network overhead and is suitable for fire rescue scenarios.

Description of drawings

FIG. 1 is a flow chart of an opportunistic forwarding method for a mobile sensor network.

detailed description

The present invention is described in further detail now in conjunction with accompanying drawing.

The main technical feature of the fire rescue scene-oriented mobile sensor network opportunistic forwarding method proposed by the present invention is a stability-based forwarding strategy, which is characterized by estimating the delivery rate of small-scale mobile nodes, large-scale mobile nodes, and firefighter nodes. , to set the proportional relationship of the three types of nodes, change the number of small-scale mobile nodes and large-scale mobile nodes (the number of firefighter nodes is usually fixed), and then use the active mobility of firefighter nodes to forward messages.

Now respectively explain as follows:

1. The stability-based forwarding strategy can calculate the node stability value and continuously update the forwarding probability. The specific content is as follows:

(1) Calculate node stability value

The stable value indicates the stability of the node's position in the network over a period of time. For the node V _k , we determine the stability by calculating the change value of its distance from its neighbor nodes. It is considered that the position of the node has not moved significantly and the smaller the change value of the distance from the neighbor node, the better the stability of the node:

Suppose the coordinates of node V _k at time t are For the set of neighbor nodes {V _k1 , V _k2 ...V _kn }, calculate the vector difference between node V _k and nodes V _k1 , V _k2 ...V _kn

The coordinates of node V _k at time t+1 are Calculate the vector difference with neighbor nodes V _k1 , V _k2 ... V _kn in turn,

First, the distance change value Δ(k, k1) between node V _k and node V _k1 is calculated from time t to time t+1 by formula (1):

In particular, if node V _k1 is not a neighbor node of node V _k at time t, then Recorded as (0,0). According to the formula (1), the distance change value between the node V _k and the neighbor nodes V _k2 ... V _kn can be calculated in turn.

Secondly, select the minimum value of the distance change between the node V _k and the neighbor node as Δ _min , and then calculate the distance change variance S ² by formula (2):

In formula (2), Δ(k, ki) represents the distance change value between node V _k and neighbor node V _ki . The variance of the distance change is expressed as the degree of deviation between the node V _k and all neighbor nodes, and then the variance is normalized as And the stability factor at time t is calculated by formula (3).

In formula (3), S _(t) represents the stability factor at time t, and there is S _(t) ∈ (0,1]. Each node maintains a stable value utility table, which shows the The size of the stable value within a certain period of time. When the nodes are in contact, the stable value of the other party will be queried, and the stable value of the node will be updated as the distance from the neighbor node changes. The update formula is shown in formula (4):

In the formula, S _old(t) represents the stability factor of the node at time t, and γ∈(0,1) represents the update constant. When S ² =0, it means that the node remains relatively static with its neighbor nodes, and the stable value of the node remains unchanged at this time; when S ² gradually increases, it means that the node becomes active gradually (the stability becomes worse).

(2) Update forwarding probability

When a node carries a message and is ready to forward it, it first broadcasts the message to be forwarded to the neighbor nodes within the communication range, and after the neighbor node receives the message, it updates the forwarding probability, and the forwarding probability is updated as shown in formula (5):

In formula (5), P _pre (V _i , V _K ) represents the forwarding probability before nodes V _i and V _k meet, and P _i represents a preset constant in the range [0,1].

2. Based on the stability of the forwarding strategy, it is also possible to set the proportional relationship of the three types of nodes by estimating the delivery rates of small-scale mobile nodes, large-scale mobile nodes, and firefighter nodes, and change the small-scale mobile nodes, large-scale The number of range mobile nodes (the number of firefighter nodes is usually fixed), and then use the active mobility capabilities of firefighter nodes to forward messages. The specific content is as follows:

(1) The proportional relationship between the number of small-scale mobile nodes n _s , the number of large-scale mobile nodes n _l and the number of firefighter nodes n _h is given as follows:

In formulas (6) and (7), CR represents the communication radius of three types of nodes, MR _H represents the moving radius of firefighter nodes, MR _L represents the moving radius of large-scale mobile nodes, and MR _s represents the moving radius of small-scale mobile nodes .

Then according to the proportional relationship between n _s , n _l , and n _h , the number of three types of nodes can be calculated:

In formula (8), the number n _h of firefighter nodes is usually fixed.

(2) Opportunistic forwarding method of mobile sensor network for fire rescue scene, as shown in Figure 1, the specific steps are as follows:

Step 1: By calculating the stable value of the nodes, the communication nodes are divided into firefighter nodes, small-scale mobile nodes and large-scale mobile nodes.

Step 2: Reasonably set the ratio between small-scale mobile nodes, large-scale mobile nodes, and firefighter nodes.

Step 3: Use the active mobility capability of firefighter nodes to forward messages during communication.

Step 4: In extreme cases, use large-scale mobile nodes to forward messages.

(3) Through the above method, the following solutions are given for different nodes:

Scenario 1: It is applicable to the situation where the firefighter node forwards the message to the mobile node in a small range and the mobile nodes in a small range forward each other. For a small-scale mobile node, the better the stability, the smaller the displacement affected by the fire environment. At this time, the small-scale mobile node acts as a stable relay node to forward the message. When a node carries a message and is ready to forward it, it broadcasts the message to be forwarded to the neighbor nodes in the communication radius. After the neighbor node receives the message, it updates the forwarding probability, and the node with high stability has a higher forwarding probability.

Scenario 2: Applicable to the situation where a large-scale mobile node forwards messages to firefighter nodes and firefighter nodes forward messages to each other. The movement of firefighter nodes is purposeful, and forwarding messages to such nodes can ensure the delivery rate of messages.

A table LIST is stored inside each node, and records are added to the table when messages are forwarded. When a large-scale mobile node carries a message and there is no forwarding record in the LIST table, the message is forwarded to nearby firefighter nodes. Every time the firefighter node forwards a message, it counts the number of surrounding nodes, calculates the ratio of firefighter nodes, small-scale mobile nodes and large-scale mobile nodes, and improves the delivery rate by changing the number of nodes Purpose.

Scenario 3: Large-scale mobile nodes are very random, and the movement rules are not obvious, so generally choose not to forward data to such nodes.

However, such nodes have the following situations:

Scenario 3.1 After a period of time, the node tends to be stable and transforms into a small-scale mobile node. For the forwarding strategy at this time, refer to Scenario 1;

Scenario 3.2 After a large-scale movement, the message cannot be forwarded. At this time, refer to Scenario 2;

Scenario 3.3 The node retains the message and forwards it directly when encountering the target node.

Firefighter nodes forward their respective messages within the range of mutual communication. Otherwise, multi-hop forwarding is carried out through nodes with high stability. To achieve the ideal forwarding effect.

It should be noted that the implementation manners under the above circumstances are only preferred manners of the present invention, and any modification made without departing from the spirit of the present invention falls within the protection scope of the present invention.

Claims (4)

1. a kind of mobile sensor network chance retransmission method towards fire rescue scene, it is characterised in that include following step Suddenly：

S1：Calculate node stationary value；

S11：Calculate the node stationary value of the sensor node of small range movement；

S12：Calculate the node stationary value of the node of fireman's composition；

S13：Calculate the node stationary value of the sensor node moved on a large scale；

S2：Proportionate relationship between calculate node；

S3：Formulate the forwarding strategy based on stability.

2. the mobile sensor network chance retransmission method according to claim 1 towards fire rescue scene, its feature It is that S1 specifically includes following steps：

A. t is calculated to the distance between t+1 moment node and node changing value；

B. choose node to be denoted as with neighbor node distance change minimum value, then calculate distance change variance；

C. it is normalized square mean, and calculates the stable factor of t；

D. node is divided into by small range mobile node, a wide range of mobile node, fireman's node according to the size of node stationary value.

3. the mobile sensor network chance retransmission method according to claim 1 towards fire rescue scene, its feature It is that S2 specifically includes following steps：

A. estimation small range mobile node, a wide range of mobile node, fireman's node are sent to rate；

B. the proportionate relationship by being sent between rate calculate node；

C. the number of three class nodes is obtained, wherein fireman's node number is fixed.

4. the mobile sensor network chance retransmission method according to claim 1 towards fire rescue scene, its feature It is that S3 specifically includes following steps：

When a. communicating message forwarding is carried out using the active locomotivity of fireman's node；

B. message forwarding is carried out using a wide range of mobile node under extreme case.