CN106900042B

CN106900042B - Sensor node of tree-type sensor network ad hoc network

Info

Publication number: CN106900042B
Application number: CN201710181118.2A
Authority: CN
Inventors: 顾敏明; 蔡昕哲; 潘海鹏
Original assignee: Hangzhou Luoman Intelligent Technology Co Ltd
Current assignee: Hangzhou Luoman Intelligent Technology Co., Ltd
Priority date: 2017-03-24
Filing date: 2017-03-24
Publication date: 2019-12-20
Anticipated expiration: 2037-03-24
Also published as: CN106900042A

Abstract

The invention discloses a sensor node of a tree sensor network ad hoc network, which adopts a method that the sensor node passively sends measurement data after receiving a coordinator instruction in the data collection process, thereby avoiding the condition of multi-node concurrence. Meanwhile, a dynamic time synchronization strategy which is relatively simple and does not need an RTC clock is used, so that the sensor node can correspondingly adjust the next sensor node wake-up time and the wireless receiving waiting time of the wireless module according to the topology condition and the topology change condition of the current network in each data collection process, the energy consumption waste caused by the premature node wake-up and the wireless long-time receiving waiting is avoided, and the service life of the network is prolonged.

Description

Sensor node of tree-type sensor network ad hoc network

The technical field is as follows: the invention relates to a wireless sensor network, in particular to a sensor node of the wireless sensor network.

Technical background:

in recent years, with the rapid development of the internet of things, wireless sensor networks begin to play more and more important roles in the lives of people. The wireless sensor network integrates multiple fields such as a sensor technology, an embedded computing technology, a modern network, a wireless communication technology, a distributed information processing technology and the like, and is widely applied to multiple application scenes such as agricultural cultivation, ecological monitoring, industrial facility detection, natural disaster prediction, intelligent traffic control, intelligent home and military occasions and the like.

The common topological structures of the wireless sensor network mainly comprise star-shaped, tree-shaped, mesh-shaped and the like topological structures. The tree-type sensor network is more suitable for the application field of wireless sensor networks which have fixed data acquisition period, small data transmission quantity, low frequency, large communication range and need regional management compared with other topological structures, but the traditional tree-type sensor network has poor dynamic topological capability in networking, the sensor nodes depend on the nodes of the previous stage, once the nodes of the previous stage fail, the nodes of the sensor nodes below the previous stage are separated from the network, meanwhile, the traditional tree-type sensor network usually adopts two aggregation methods in data aggregation, namely, the sensor nodes are dormant from low power consumption according to fixed time intervals, and wake up randomly for a period of time after the environmental parameters are measured, actively sending data; and secondly, the sensor node is awakened from dormancy according to a fixed time interval, waits for a convergence instruction after the environmental parameter measurement is completed, and passively sends data. The former is easy to generate the concurrency of a plurality of node data, which causes message collision and needs to be retransmitted for a plurality of times, thus wasting redundant energy consumption, and the latter is used for ensuring that the node can receive the collection instruction, the node needs to be awakened in advance for a long time, thus wasting redundant energy consumption.

The invention content is as follows:

aiming at the problems, the invention designs the sensor node of the tree-type sensor network ad hoc network which meets the actual requirements, and realizes low power consumption during data collection.

A sensor node of a tree-type sensor network ad hoc network comprises a power supply module, a 433M wireless module, a low-power processor and a sensor module, wherein the working steps of the sensor node comprise a first network access stage, a second network access stage and a data measurement and transmission stage; the method comprises the following specific steps:

1) initializing hardware configuration after the node is electrified;

2) reading self node address information in an EEPROM in a controller chip, wherein the default address is 0X 0000;

3) judging whether the node address is 0X0000, if so, judging that the node is a new node which is not networked, and entering a stage that the node is accessed into the network for the first time, namely step 4-7, otherwise, judging that the node is not a new node, and entering step 8;

4) broadcasting a new node request network access instruction in a channel 0, wherein the new node request network access instruction comprises the address of a node and the category of a sensor;

5) switching to a channel 0 receiving state, waiting for reply, wherein the waiting time is T _ Wait, judging whether a new node network access allowing instruction replied by the coordinator is received, if so, entering a step 6, otherwise, returning to the step 4;

6) reading a new node network access permission instruction, recording a node address distributed by the coordinator, writing the node address into an EEPROM, recording a use channel, marking the self state as a normal state, and marking the network access just now;

7) replying a node confirmation network access instruction to the current coordinator in the channel 0, and entering the step 8;

8) judging whether the self state is a fault state, if so, entering a network re-access stage, namely step 9-18, otherwise, entering a data measurement sending stage, namely step 19-28;

9) judging whether the broadcasting frequency of the network access request command of the original node reaches the specified frequency, if so, entering a step 14, otherwise, entering a step 10;

10) broadcasting an original node network access request instruction in a channel 0;

11) switching to a channel 0 receiving state, waiting for replying, wherein the waiting time is T _ Wait, whether an original node network access permission instruction replied by an original coordinator is received or not, if yes, entering a step 12, and otherwise, entering a step 13;

12) marking the self as a normal state, marking the network access, recording the use channel in the command, returning to the step 8,

13) randomly waiting for a period of time, and returning to the step 9;

14) broadcasting a network access request instruction of a node to be managed in a channel 0;

15) switching to a channel 0 receiving state, waiting for a reply, wherein the waiting time is T _ Wait, whether a network access instruction of the node to be managed replied by the coordinator is received or not is judged, if yes, the step 16 is carried out, and if not, the step 18 is carried out;

16) reading an instruction, recording a use channel, marking the self state as a normal state, and marking the network access just now;

17) replying a network access confirmation instruction of the node to be managed to the hosting coordinator in the channel 0, and returning to the step 8;

18) waiting for 30 seconds, resetting the broadcast times of the network access request instruction of the original node, and returning to the step 9;

19) judging whether the network is just accessed, if so, entering a step 20, otherwise, entering a step 22;

20) assigning all the measurement data to 0;

21) switching to a using channel receiving state, waiting for a data acquisition instruction sent by a coordinator in the existing network, and entering step 24 after receiving the instruction;

22) turning on a power supply of the sensor module, and measuring environmental parameters;

23) turning off a power supply of a sensor, waking up a wireless module, switching to a channel receiving state, waiting for a coordinator instruction, wherein the waiting time is T _ Wait _ Collect, judging whether a data acquisition instruction sent by the coordinator is received, if so, entering step 24, and otherwise, entering step 28;

24) recording the time interval T _ Collect for collecting data next time, the total number N _ Error of fault nodes and the number N _ Error _ Add of newly-added fault nodes, and calculating the awakening timing time T _ Wake of the low-power-consumption processor next time, namely T _ Collect-T _ Measure- (N _ Error _ Add) T _ Wait). After the wireless module is awakened, receiving a waiting time length T _ Wait _ Collection ═ N _ Error ═ T _ Wait, and timing T _ Wake by a timer;

25) sending a measurement data instruction to a coordinator sending node by using a channel;

26) closing all unused resources and entering dormancy;

27) after the timing time T _ Wake is up, the timer interrupts to Wake up the low-power-consumption processor, and the step 8 is returned;

28) and marking the self fault state and returning to the step 8.

The invention adopts the method that the sensor node passively sends the measurement data after receiving the coordinator instruction in the data collection process, thereby avoiding the condition of multi-node concurrence. Meanwhile, a dynamic time synchronization strategy which is relatively simple and does not need an RTC clock is used, so that the sensor node can correspondingly adjust the next sensor node wake-up time and the wireless receiving waiting time of the wireless module according to the topology condition and the topology change condition of the current network in each data collection process, the energy consumption waste caused by the premature node wake-up and the wireless long-time receiving waiting is avoided, and the service life of the network is prolonged.

Description of the drawings:

FIG. 1 is a diagram of a sensor node hardware architecture.

Fig. 2 is a hardware configuration diagram of the coordinator.

Fig. 3 is a diagram of a tree network architecture.

Fig. 4 is a general flow chart of the sensor node operation.

Fig. 5 is a flow chart of a stage of a node accessing a network for the first time.

Fig. 6 is a flow chart of a node re-network-entry stage.

Fig. 7 is a flow chart of a node data measurement transmission phase.

The specific implementation mode is as follows:

the following further illustrates the methods and principles of the present invention in connection with examples and the accompanying drawings.

The sensor node and the coordinator are in wireless communication through 433M, and the coordinator is in serial communication with the relay gateway.

Sensor node (node for short): and the system is responsible for measuring various environmental data in the field and wirelessly transmitting the data to the coordinator through 433M.

The sensor node is composed of a power supply module, a 433M wireless module, a low-power consumption processor and a sensor module, and a hardware structure diagram is shown in fig. 1.

The power module supplies power to the other three modules, and the low-power processor can cut off the power supply of the sensor module. Data transmission is carried out between the low-power-consumption processor and the 433M wireless module through an SPI bus, and the low-power-consumption processor and the sensor module carry out data transmission through an IIC bus or an ADC according to different sensors.

The coordinator: on one hand, the sensor node wirelessly communicates with the sensor node through 433M, and is responsible for establishing a sensor network and acquiring measurement data of the sensor node. And on the other hand, the system is communicated with the relay gateway through a serial port and is responsible for forwarding the measurement data of the sensor node to the relay gateway and receiving the instruction of the relay gateway.

The coordinator is composed of a power module, a 433M wireless module, a low-power consumption processor and a sensor module, and a hardware structure diagram is shown in FIG. 2.

Wherein, the power module supplies power for other two modules. Data transmission is carried out between the low-power processor and the 433M wireless module through the SPI bus.

Relay gateway (gateway for short): after the measured data of each node is collected in the relay gateway, the data are fused by the gateway, and finally the data are sent to the monitoring server through the wireless network.

The structure of the tree network formed by the sensors, the coordinator, the relay gateway and the monitoring server host is shown in fig. 3.

The monitoring server host serves as a first layer of the tree network, each relay gateway corresponds to one coordinator and serves as a second layer of the tree network, and the sensor nodes serve as a third layer of the tree network.

Name interpretation:

if the node A does not join any nodes of the network, the node A is called a new node. When a new node a is added to the network of coordinator a, node a is said to be the existing node of coordinator a, and coordinator a is the existing coordinator of node a. When the existing node A is disconnected from the network due to the fault, the node A is called as the original node of the coordinator A, and the coordinator A is the original coordinator of the node A. When an original node a of the coordinator a joins the network of the coordinator B, the node a is called a hosting node of the coordinator B, the coordinator B is called a hosting coordinator of the node a, and the node a is called a hosted node of the coordinator a (belonging to the category of the original node).

The operation state of the sensor node is divided into two states: a state of no networking or networking but disconnection from the coordinator (referred to as a fault state for short); networking and connecting with the coordinator in a normal state (referred to as a normal state for short).

The response waiting time after the coordinator and the node send data outwards is T _ Wait, and the coordinator and the node do not Wait after overtime. The waiting response time T _ Wait is determined according to the time required by a single response in practical application.

The node is accessed to the network for the first time and is accessed to the network again, the wireless channel is a channel 0 (broadcast channel), and the wireless channel is a use channel of the corresponding network in the data measurement and transmission stage.

Sensor node workflow: the method mainly comprises a first network access stage, a second network access stage and a data measurement and transmission stage.

Note 1: except that the new node which is not accessed to the network receives the network access permission instruction, the other nodes can only receive the coordinator instruction of which the node address conforms to the self address in the instruction.

Note 2: in the broadcast monitoring stage, the coordinator receives and transmits commands and uses a channel 0 (broadcast channel); in the data gathering stage, the coordinator sends and receives instructions to use the use Channel _ Used selected in the network access stage of the coordinator.

1. And after the node is powered on, hardware configuration is initialized.

2. And reading self node address information (the default address is 0X0000) in the EEPROM in the controller chip.

3. And if the node address is 0X 0000?, judging that the node is a new node which is not networked, and entering a stage that the node is accessed into the network for the first time (step 4-7), otherwise, judging that the node is not the new node, and entering step 8.

First access network phase (step 4-7):

4. a new node request network entry command (containing the node's address and sensor class) is broadcast on channel 0 (broadcast channel).

5. And switching to a channel 0 receiving state, waiting for replying, wherein the waiting time is T _ Wait, and judging whether a command (containing the allocated node address and the used channel)? for allowing the new node to enter the network is received or not by the coordinator, if so, entering a step 6, otherwise, returning to the step 4.

Note 1: the waiting time T _ Wait is determined according to the time required by the 433M radio module to answer a single time actually adopted.

Note 2: the node address (2 bytes) is composed of a gateway address (1 byte) and a network access sequence number (1 byte). This has the advantage that the network configuration information, i.e. the gateway address and the network number of the connection, can be known from the node address.

6. And reading a network access permission instruction of the new node, recording the node address distributed by the coordinator, writing the node address into an EEPROM, and recording the use channel. And marking the self state as a normal state and marking the network access just now.

Note 1: the node address is written into the EEPROM to ensure that the original network structure information can still be maintained after the node is powered off.

Note 2: the channel is not written into the EEPROM because the coordinator fails to power down, the channel is required to be reselected to establish a network after being powered up again, and it is meaningless to write the channel in the EEPROM.

7. Replying the node confirmation network-accessing command (containing the node address) to the current coordinator in the channel 0. Step 8 is entered.

8. Whether the self status is the failure status?, if yes, enters the re-access network phase (steps 9-18), otherwise enters the data measurement sending phase (steps 19-28).

Re-access network phase (steps 9-18):

(attempt to connect the original coordinator)

9. And (4) judging whether the broadcasting times of the original node request network access instruction (including the address and the sensor type of the node) reach the specified times (which can be set according to requirements)?, if so, entering step 14, otherwise, entering step 10.

10. And broadcasting a network access request instruction (including the address and the sensor category of the node) of the original node in the channel 0.

11. And switching to a channel 0 receiving state, waiting for replying, wherein the waiting time is T _ Wait, and whether an original node network access permission instruction (including a node address and a used channel)? replied by the original coordinator is received, if yes, entering a step 12, and otherwise, entering a step 13.

12. Marking the self as a normal state, marking the network access just now, and recording the use channel in the command. And returning to the step 8.

13. And randomly waiting for a period of time and returning to the step 9.

(request other coordinator to host)

14. And broadcasting a network access request instruction (including the address and the sensor category of the node) of the node to be managed in the channel 0.

15. And switching to a channel 0 receiving state, waiting for a reply, wherein the waiting time is T _ Wait, whether a command? for allowing the to-be-hosted node to access the network (including the node address and the used channel) replied by the coordinator is received, and if yes, entering a step 16, otherwise, entering a step 18.

16. Reading the instruction and recording the used channel. And marking the self state as a normal state and marking the network access just now.

17. And replying an confirmed network access instruction (containing a node address) of the node to be managed to the management coordinator in a channel 0. And returning to the step 8.

18. And waiting for 30 seconds (set according to needs), and clearing the broadcasting times of the network access request instruction of the original node. Returning to step 9.

Data measurement transmission phase (steps 19-28):

19. and judging whether to just enter the network?, if so, entering the step 20, and otherwise, entering the step 22.

20. All measurement data are assigned a value of 0.

Note: the first data transmission phase after accessing the network is only for time synchronization with the coordinator and does not measure the environment data.

21. And switching to a channel receiving state, and waiting for a data acquisition instruction (comprising a node address, a next data acquisition time interval T _ Collect, a total number of failed nodes N _ Error and a number of newly-added failed nodes N _ Error _ Add) sent by a coordinator in the existing network. After receiving the command, the process proceeds to step 24.

Note: the reception status waits all the time because the time between the node just accessed the network and the coordinator is not synchronized.

22. And (4) turning on a power supply of the sensor module, and measuring the environmental parameters.

23. The power supply of the sensor is turned off, the wireless module is awakened, the receiving state is switched to the using channel, the command of the coordinator is waited, the waiting time is T _ Wait _ Collect, whether the data acquisition command? sent by the coordinator is received or not is judged?, if yes, the step 24 is carried out, otherwise, the step 28 is carried out.

24. Recording the time interval T _ Collect for collecting data next time, the total number N _ Error of fault nodes and the number N _ Error _ Add of newly-added fault nodes, and calculating the awakening timing time T _ Wake of the low-power-consumption processor next time, namely T _ Collect-T _ Measure- (N _ Error _ Add) T _ Wait). After the wireless module wakes up, the wireless module receives a waiting time length T _ Wait _ Collet ═ N _ Error ═ T _ Wait. The timer times T _ Wake.

Note: t _ Measure is the sum of the time required by the sensors on the nodes to Measure data and is determined by the types and the number of the sensors owned by the actual nodes. The reason for subtracting T _ Measure when calculating T _ Wake is that the time T _ Measure is needed for the sensor module to Measure the environmental data, so the node needs to Wake up the measurement by T _ Measure in advance.

Note 2: the N _ Error _ Add _ T _ Wait is subtracted when calculating T _ Wake because the next data acquisition is reduced by N _ Error _ Add nodes from this time, resulting in the next data acquisition instruction sent by the coordinator reaching the time of N _ Error _ Add T _ Wait earlier than this time.

Note 3: the reason why N _ Error × T _ Wait is added when T _ Wait _ Collect is calculated is that at most N _ Error nodes may return to normal from a fault state before the next data collection is reached, resulting in the next data collection instruction arriving at the latest N _ Error × T _ Wait time at most.

25. The measurement data command (containing the node address and the measurement data) is sent to the coordinator sending node by using the channel.

26. And closing all unused resources and entering dormancy.

27. And after the timing time T _ Wake is up, the timer is interrupted to Wake up the low-power-consumption processor. And returning to the step 8.

28. And marking the self fault state and returning to the step 8.

Claims

1. A sensor node of a tree-type sensor network ad hoc network is characterized by comprising a power supply module, a 433M wireless module, a low-power processor and a sensor module;

the working steps of the sensor node comprise a first network access stage, a second network access stage and a data measurement and transmission stage; the method comprises the following specific steps:

1) initializing hardware configuration after the node is electrified;

13) randomly waiting for a period of time, and returning to the step 9;

20) assigning all the measurement data to 0;

24) recording a time interval T _ Collect for collecting data next time, a total number N _ Error of fault nodes and a number N _ Error _ Add of newly-added fault nodes, calculating the awakening timing time T _ Wake of a low-power-consumption processor next time, receiving the awakening time T _ Wait _ Collet of a wireless module, and timing T _ Wait by a timer;

26) closing all unused resources and entering dormancy;

28) and marking the self fault state and returning to the step 8.