CN103957031B - Frequency hopping based on linear wireless sensor network and the implementation method of positioning function - Google Patents

Abstract

The invention designs a method for realizing the frequency hopping and positioning functions based on the linear wireless sensor network, which can further enhance the anti-interference performance and readability of the linear wireless sensor network. Frequency hopping includes three methods, namely adaptive frequency hopping, active frequency hopping and passive frequency hopping. Adaptive frequency hopping can make the entire wireless network analyze channel interference more intelligently and change the current communication channel. Active frequency hopping can ensure the current The network can change the communication channel of the current network by the administrator. The passive frequency hopping method is used for the wireless network node to query the current available channel and change it when the network is interrupted, so as to enhance the reliability of the network. The situation adopts different frequency hopping methods. The positioning function is based on the loss formula of electromagnetic waves in free space and the loss power to calculate the distance between the receiver and the sender for positioning.

Description

Implementation method of frequency hopping and positioning function based on linear wireless sensor network

technical field

The present invention designs a method that can realize frequency hopping and positioning functions in a linear wireless sensor network. This method can enhance the anti-interference performance of the entire network, ensure stable and reliable communication of the network, and facilitate the controller to quickly grasp the wireless sensor nodes. geographical topology.

technical background

In the process of rapid economic development in my country, transportation lines related to the lifeline of the country's economy, such as highways at all levels, communication lines, power lines, and oil and gas pipelines, usually need to grasp information about the operating conditions of each part in a timely manner, and these lines usually have remote locations. , the topological structure is linear, the distribution distance is wide, and it is difficult for the staff to know the location of the accident at the first time. Therefore, the linear wireless sensor network can be used in these pipelines so that the managers can quickly and timely grasp the operation of the entire pipeline. . The addition of the frequency hopping function can ensure the anti-interference performance of the entire wireless sensor network, and the positioning function can facilitate the administrator to quickly understand the distribution of wireless nodes in the network.

Contents of the invention

The invention designs a method for realizing the frequency hopping and positioning functions of the wireless sensor network communication protocol, and the frequency hopping modes mainly include self-adaptive frequency hopping, active frequency modulation and passive frequency modulation.

The linear wireless sensor network is composed of linearly distributed network nodes whose physical addresses are sequentially from 1 to N, where N is a natural number. The network node with a physical address of 1 is called a control node, and the rest of the nodes are called data acquisition nodes. The distance between nodes increases as the physical address increases, and the number of network nodes can be increased or decreased as needed.

Linear wireless sensor networks only allow communication between adjacent nodes, where adjacent nodes are nodes with adjacent physical addresses, and communication across multiple network nodes must be completed by adjacent network nodes.

There are M channels in the entire network. When adaptive frequency hopping is used, each network node regularly detects the strength of the interference signal under the current network channel. When a network node sees that the strength of the interference signal is greater than a certain threshold, it sends a message to the control node. The frequency hopping request data packet, wherein the threshold value can be set according to the actual environment. When the control node accumulatively receives 3 or more frequency hopping request data packets, it indicates that the interference in the current network channel is serious and frequency hopping is required. The control node sends a frequency hopping traversal data packet, the destination physical address is N, and each network node in the backward transfer communication with the physical address ranging from 1 to N performs the following operations after receiving the frequency hopping traversal data packet: first, sequentially detect M The interference signal strength of the channel, and then these strength values are accumulated with the interference strength value in the channel corresponding to the data packet, and finally the data packet is passed backward until the network node with the power address N receives and executes the above steps, through Compare the interference value of each channel and find the channel X with the smallest interference value, the component frequency hopping executes the data packet and writes channel X into the data packet, and performs the forward transfer communication process with the physical address from N to 1. In this process, each After the network node receives the frequency hopping execution data packet, it performs the following operations: first, send the frequency hopping execution data packet to the next network node forwarded, and after confirming that the transmission is successful, change the communication channel of its own network node to the X channel until the control After the node receives the frequency hopping execution data packet and changes its own channel to X channel, the adaptive frequency hopping work of the whole network is completed.

When the active frequency modulation method is adopted, the control node performs backward transmission after receiving the active frequency hopping data packet sent by the computer, and the destination physical address is N, and each node in the backward transmission directly receives the active frequency hopping data packet Carry out backward forwarding until the network node with the physical address N receives the active frequency hopping data packet, extracts the channel Y, constructs the frequency hopping execution data packet, writes the channel value Y into the data packet and then forwards it, and confirms that the transmission is successful Change the current communication channel to Y, and each network node in the forward transmission process will perform forward transmission after receiving the frequency hopping execution data packet. After confirming that the transmission is successful, change the communication channel to Y until the control node receives the frequency hopping execution data packet. After executing the data packet, change the communication channel to Y, and the active frequency hopping of the entire network is completed.

When passive frequency hopping is used, the node sends a probe request ACK packet to the previous node at regular intervals. If the ACK cannot be received, it means that the node cannot communicate with the previous node normally and passive frequency hopping is required. Now the network The communication channel of the node is changed to 1, and the request ACK packet is formed, the destination address is the physical address of the network node -1, and then forwarded. If no ACK is received, the communication channel is +1 and the request ACK packet is forwarded again until Until the receiver's ACK is received, the passive frequency hopping is completed.

The invention designs a method for realizing the distance positioning function of network nodes. Since the network topology is linear, the distance between any two network nodes is equal to the sum of the distances between any two network nodes. The principle of calculating the distance between adjacent nodes is to calculate the power loss according to the transmit power and receive power in the data packet sent by the sender, and use the loss formula of electromagnetic waves in free space:

Los(dBm)＝32.44+20lgd(Km)+20lgf(MHz)

Given the known transmission frequency f, the distance d between adjacent network nodes is calculated from the power loss.

When the control node receives the command from the computer to request the distance information of the network node, the component requests the location data packet, the destination address is N, and initializes the space of N bytes in the data packet to store the distance information between the corresponding two nodes , in the backward transfer, each node calculates the distance information according to the sending power and receiving power after receiving the request position data packet, writes it into the corresponding position of the request position data packet, and continues the backward transfer, when the physical address is N network After the node receives the requested location data packet, it writes its corresponding distance information and transmits it back and forwards it. In the forward transmission, each network node receives the requested location data packet, calculates the distance information again and compares it with the initial distance information. After the average value is calculated, it is covered to the corresponding position until the control node receives the request position data packet again and completes the above operations and then sends the distance information to the computer, thus obtaining the distance information of the entire network.

Description of drawings

Figure 1 is a topology diagram of the entire linear wireless sensor network

Figure 2 is the control node adaptive frequency hopping flow chart

Figure 3 is a flowchart of data acquisition node adaptive frequency hopping

Figure 4 is a flow chart of the active frequency hopping of the control node in the whole network

Figure 5 is a flow chart of active frequency hopping of data collection nodes in the whole network

Figure 6 is a flowchart of passive frequency hopping of network nodes

Figure 7 is a schematic diagram of a network node requesting location information

detailed description

The present invention is based on the design and implementation of the linear wireless sensor network communication protocol. This linear wireless sensor network adopts a four-layer protocol architecture, which is respectively the physical radio frequency layer, the media access control layer, the network layer and the user application layer. The development work of the present invention is mainly It is carried out at the network layer and user application layer.

The applicable network topology of the present invention is linear (see Fig. 1), and the physical address is from 0x01 to 0xN, wherein the size of N can be set by itself according to the size of the specific network, and the network node whose physical address is 0x01 is a control node, which can communicate with the computer Information interaction work is the initial node that actively initiates network control information, and is also the core of the entire wireless sensor network. The other network nodes are data collection nodes, responsible for data collection in the linear network. The physical addresses of all network nodes have been written into the chip registers before use, and are deployed in order of physical addresses from small to large during deployment.

The interaction between the application layer and the network layer is through the port number in the data packet, hereinafter referred to as PORT. After receiving the data packet, the receiver completes the corresponding user application layer function by analyzing the PORT of the data packet.

The specific implementation manner of adaptive frequency hopping among the present invention is: (refer to Fig. 2 and Fig. 3) set the threshold value P that initiates adaptive frequency hopping, the size of P value can be voluntarily according to the specific situation of geographical environment and the tolerance degree to communication interference Setting, each node in the network will pass the received signal strength value in the register every once in a while, hereinafter referred to as RSSI, if the RSSI is greater than P, the component frequency hopping request data packet, the port number is 0xf0, the destination address is 0x01, and then proceed Forwarding, each node in the forward transmission only performs forward forwarding when it receives the data packet with the port number 0xf0. The frequency hopping of the whole network is started when the data packets of this port number have been received 3 times in total. When the number of data packets reaches 3, the control node constructs the whole network frequency hopping data packet, the port number is 0xf1, writes the RSSI in each channel into the data packet, and the destination address is 0xN, and forwards it backward. In the backward transmission, each network node receives the data packet with the port number 0xf1, and then accumulates the RSSI in each channel to the corresponding part of the data packet and then forwards it backwards until the network node with the physical address 0xN transfers the RSSI value in each channel After the accumulation is completed, the channel X with the smallest RSSI is obtained by comparison, and a frequency hopping execution data packet is formed, the port number is 0xf2, and the destination address is 0x01, and forwarded. Each network node in the forward transfer forwards forward after receiving the data packet whose port number is 0xf2, and changes the current communication channel to X after confirming receipt of the ACK from the forward adjacent node. When the control node receives the data packet with port number 0xf2 and changes the current communication channel to X, the whole adaptive frequency hopping work is completed.

The specific implementation of active frequency hopping in the present invention is: (refer to Figure 4 and Figure 5) when the network manager finds that there is relatively serious interference in the network, the computer can initiate active frequency hopping instructions to the control node, and formulate frequency hopping to channel Y, the control node establishes an active frequency hopping data packet after receiving the instruction, the channel Y writes the data packet, the port number is 0xf3, the destination address is 0xN, and forwards backward. After the network node in the backward transmission receives the data packet with port number 0xf3, it does not perform any processing and only forwards it backwards until the network node with the physical address of 0xN receives the active frequency hopping data packet and then constructs the frequency hopping execution data packet. Channel Y writes data packets, the port number is 0xf2, and the destination address is 0x01, which is forwarded. Each network node in the forward transfer forwards forward after receiving the data packet whose port number is 0xf2, and changes the current communication channel to Y after confirming receipt of the ACK from the forward adjacent node. When the control node receives the data packet with port number 0xf2 and changes the current communication channel to Y, the whole active frequency hopping work is completed.

The specific embodiment of passive frequency hopping among the present invention is: (referring to Fig. 6) network node sends request ACK data packet forward to adjacent node every period of time, when can't receive ACK, represent and adjacent node work in different On the communication channel, passive frequency hopping is required to synchronize with the channel of the adjacent node. First, set the current channel to 1, form a request ACK packet, and forward it forward. If the ACK still cannot be received, increase the channel by 1, and repeat the above The steps until the ACK is received indicate that the current communication channel is synchronized with the communication channel of the forward adjacent node, and the passive frequency hopping work is completed.

The specific implementation manner of the positioning function of the present invention is: (referring to Fig. 7) because the topological structure of the whole network is a linear structure, to obtain the distance between any two network nodes only need to obtain the distance between each adjacent network node therebetween After the distance information can be obtained by adding. When the manager needs to obtain the distance location information of the entire network, the computer sends a request location instruction to the control node, and the control node constructs a request location data packet after receiving the instruction, the port number is 0xf4, the destination address is 0xN, and the transmission power is written. A distance information space with a size of N bytes is reserved in the data part of the data packet to store the distance information for backward forwarding. After receiving the data packet with port number 0xf4 and destination address 0xN, the network node in the backward transmission calculates the power loss according to the sending power and receiving power, according to the loss formula of electromagnetic waves in free space:

Los(dBm)＝32.44+20lgd(Km)+20lgf(MHz)

The wireless sensor network communication protocol uses a frequency of 433MHZ. The distance d of adjacent nodes can be calculated from the power loss, and written into the distance information space of the corresponding field in the corresponding data packet and forwarded backward. When the physical address is 0xN After the network node receives the data packet with the port number 0xf4 and completes the above operations, it changes the destination address in the data packet to 0x01 and forwards it forward. The network node in the forward transmission receives the port number 0xf4 and the destination address is 0x01 After the data packet, add the calculated distance d to the distance information at the corresponding position, divide it by 2 to get the average value, and then write it into the corresponding byte, which will be regarded as the distance information finally delivered to the control node, and the previous to forward. After the control node receives the data packet with the port number 0xf4 and the destination address 0x01, it first performs the above operations, and then sends the distance information of N bytes in the data packet to the computer, so that the administrator can use the distance information sent by the control node information to understand the geographical distribution of the entire wireless sensor network.

Claims (1)

1. frequency hopping based on linear wireless sensor network and the implementation method of positioning function, it is characterised in that:

1) linear wireless sensor network is made up of the wireless network node of N number of linear array, and physical address is followed successively by 1,2,3...N, wherein N is natural number, physical address be 1 wireless network node become main controlled node, its Remaining wireless network node becomes data acquisition node；

2) radio communication is only limitted between the wireless network node of contiguous physical address carry out, non-adjacent physical address Communication between wireless network node must be completed by the wireless network node relay of contiguous physical address；

3) implementation method of frequency hopping function based on linear wireless sensor network, can strengthen linear wireless senser The interference free performance of network, adapts to communication environment complicated and changeable, and frequency hopping function is realized by three kinds of modes, Including AFH, actively frequency hopping and passive frequency hopping, different frequency hopping sides can be selected according to actual environment Formula；

A) AFH: wireless network node is in an idle state every the interference of surrounding of detection in 1 second Value, sends request frequency-hopped data bag when interference value is more than the threshold value arranged to main controlled node, and main controlled node is first Secondary receiving asks beginning timing after frequency-hopped data bag, and the request frequency-hopped data bag that in 10s, accumulation receives is more than 3 Time send the whole network frequency-hopped data bag, rear in communication process, wireless network to linear wireless sensor network The interference value of all channels is write the whole network frequency-hopped data bag by node, wherein, backward incremental for physical address, Linear wireless sensor network has a M channel, and respectively 1,2,3...M, physical address is the wireless network of N Network node obtains, by comparing, the channel X that interference value is minimum, and write frequency hopping performs packet and carries out forward direction and lead to Letter, wherein, X is natural number, and forward communications is that physical address successively decreases, the wireless network node in forward communications Present channel is skipped to channel X；

B) actively frequency hopping: network manager sends actively frequency hopping instruction to main controlled node, indicates linear wireless senser Network frequency hopping is to channel X, and main controlled node is by channel X write actively frequency-hopped data bag and carries out backward communication, thing Manage after the wireless network node that address is N receives active frequency-hopped data bag and carry out forward communications, in forward communications Wireless network node present channel is skipped to channel X；

C) passive frequency hopping: send request ACK to the wireless network node that forward direction is adjacent every 1 minute wireless network node Packet, retransmits this packet in 5 seconds after not receiving ACK, should after not receiving ACK for continuous 3 times Wireless network node performs passive frequency hopping, and the channel of wireless network node is switched on M execution successively by 1 State process, after a certain channel receives ACK, stop passive frequency hopping；

4) realization of positioning function based on linear wireless sensor network, can make network manager quickly grasp nothing The location distribution situation of line network node, it is characterised in that wireless network node is according to receiving power and sending out Power is sent to draw packet power attenuation in communication process, and according to electromagnetic wave merit in free space Rate loss formula Los (dBm)=32.44+20lgd (Km)+20lgf (MHz) draws range information, and in formula, Los is Electromagnetic wave in the loss of free space, its unit be decibel (dBm), d be electromagnetic transmission distance, its Unit be km (Km), f be wave frequency, its unit is megahertz (MHz).