KR20150086736A - Topology control method of wireless sensor network in vehicle - Google Patents

Abstract

The present invention relates to a topology control method of a wireless sensor network in a vehicle. The present invention includes the steps of: configuring a topology between sensor nodes and a base station which comprise a wireless sensor network; detecting remaining battery when the sensor node receives a specific control order from the base station; checking whether the detected remaining battery is below a reference value; and reconfiguring the topology by the sensor node using neighboring nodes if the detected remaining battery is below the reference value. Therefore, the sensor node can use the remaining battery efficiently.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a topology control method for a wireless sensor network in a vehicle,

The present invention relates to a topology control method of an in-vehicle wireless sensor network that enables each sensor node constituting a wireless sensor network in a vehicle to efficiently use the remaining battery by reconfiguring the network topology when the battery remaining amount is insufficient, .

Generally, the vehicle system provides safety and convenience-related services to the driver. Problems with these systems can directly cause damage to the driver, as well as expose pedestrians and other vehicles to vehicle accidents, posing a significant safety hazard.

Conventional wireless sensor network-based vehicle systems maintain an initially configured network topology without considering the remaining battery level despite the insufficient battery power. For example, when the initial topology of a wireless sensor network is configured with a star topology, each sensor node continues to transmit sensor information to the base station even when the remaining battery power is insufficient. Therefore, when the battery is completely discharged, the sensor node stops its operation and adversely affects the normal operation of the vehicle system, and inefficiently uses its own battery.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the problems of the prior art described above, and it is an object of the present invention to provide a wireless sensor network in which each sensor node of a vehicle checks its own remaining battery level to reconstruct a network topology, The present invention also provides a method of controlling a topology of a wireless sensor network in a vehicle.

According to another aspect of the present invention, there is provided a method of controlling a topology of a wireless sensor network in a vehicle, the method comprising: configuring a topology between a base station and sensor nodes constituting a wireless sensor network; Detecting a remaining battery level when the sensor node receives a specific control command from the base station; checking whether the remaining battery level detected by the sensor node is less than or equal to a reference value; And the node is reconfiguring the topology using the neighboring node.

The topology configuration step may include a star topology directly connected between the base station and each sensor node.

The topology configuration step may further include entering the sleep mode of the sensor node when the topology is configured.

Further, the specific signal is an operation stop command transmitted from the base station.

The topology reconfiguration step may include: transmitting the node status information to the base station by the sensor node; searching for one or more neighbor nodes by the sensor node; Selecting one of the searched neighboring nodes based on the link quality index, and establishing a connection with the selected neighboring node by the sensor node.

The transmitting of the node status information may include transmitting node status information including the battery remaining amount information and topology reconfiguration notifying information to the sensor node when the detected remaining battery level is less than a reference value, And informing the driver of a shortage of the remaining battery power of the sensor node that has transmitted the node status information upon receiving the information.

The neighboring node search step may include broadcasting the active scan request by the sensor node and transmitting a beacon frame to a neighboring node that receives the active scan request.

In addition, the beacon frame transmitting step may include transmitting the beacon frame including the battery remaining amount, the link quality index, and the sensor information of the neighboring node receiving the active scan request to the beacon frame.

The neighboring node selecting step may include calculating battery efficiency of each of the neighboring nodes searched by summing up the battery remaining amount and the link quality index of the searched neighboring node and comparing the calculated battery efficiencies of the searched neighboring nodes, And selecting the neighboring node having the highest battery efficiency among the searched neighboring nodes.

The battery efficiency calculation step may be performed by assigning weights to the battery remaining amount and the link quality index, respectively.

Further, in the battery efficiency calculating step, the sensor node sets a higher weight to the battery remaining amount than the link quality index.

Further, the present invention is characterized in that, after the topology is reconfigured, the sensor node further transmits the remaining battery level information and sensor information to the neighbor node.

In the present invention, each sensor node constituting a wireless sensor network in the vehicle checks its remaining battery level and reconstructs the network topology using neighboring neighbor nodes when battery power is insufficient. Therefore, the present invention can reduce the battery consumption of the sensor nodes in the wireless sensor network and efficiently use the remaining battery power.

Also, the present invention provides the battery remaining amount information of the corresponding sensor node to the driver when the battery remaining amount of the sensor node in the in-vehicle wireless sensor network is insufficient, thereby allowing the driver to recognize the insufficient battery remaining amount of the sensor node, .

1 is a block diagram illustrating a wireless sensor network system in a vehicle according to an embodiment of the present invention;
FIG. 2 is a flowchart illustrating a topology reconfiguration method of a wireless sensor network system according to an embodiment of the present invention; FIG.
FIG. 3 is a flow chart illustrating the topology reconfiguration process shown in FIG. 2; FIG.
4 is an exemplary diagram illustrating a reconstructed topology in accordance with an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a configuration diagram illustrating a wireless sensor network system in a vehicle according to an embodiment of the present invention. In this embodiment, the in-vehicle wireless sensor network system may be a vehicle system such as a parking assist system based on a wireless sensor network.

1, the wireless sensor network system includes a base station (BS) 0 and one or more sensor nodes (SN) 1 to 8 connected to a wireless sensor network . Here, the wireless sensor network may be composed of a star topology that is directly connected between the base station 0 and each of the sensor nodes 1 to 8. In this embodiment, the wireless sensor network is configured as a star topology. However, the present invention is not limited to this, and the topology can be changed according to the service type.

The base station (0) performs wireless communication with one or more sensor nodes (1 to 8). Here, the base station 0 can be supplied with power at all times from the vehicle.

The base station (0) transmits a control command according to the operating condition of the system. Here, the control command may be an operation command, an operation stop command, or the like.

The base station (0) continuously monitors the status of the sensor nodes (1 to 8). In other words, the base station 0 continuously monitors the battery level of the sensor nodes 1 to 8 and whether the topology is reconfigured.

The sensor nodes 1 to 8 are disposed on the front and rear sides of the vehicle and have a battery (not shown) for supplying power to the sensors themselves. At this time, the sensor nodes 1 to 8 may be disposed at arbitrary positions according to the in-vehicle system and service.

The sensor nodes 1 to 8 are composed of sensors such as an image sensor, an infrared sensor, and an ultrasonic sensor, and transmit the sensor information to the base station 0 by sensor information sensed by the sensors. For example, the sensor node SN transmits an image photographed through the image sensor to the base station (0).

When the sensor nodes 1 to 8 receive the operation stop command from the base station 0, the sensor nodes 1 to 8 detect the current remaining battery level of the battery. Then, the sensor nodes 1 to 8 check whether the detected remaining battery level is below the reference value.

The sensor nodes 1 to 8 reconfigure the topology based on the current battery remaining amount and link quality index (LQI) information of neighbor nodes (NN) in the wireless sensor network if the battery remaining amount is less than the reference value . In other words, the problem node whose battery remaining amount is equal to or less than the reference value performs wireless communication with the base station 0 through cooperative communication with the neighboring node.

2 is a flowchart illustrating a topology reconfiguration method of a wireless sensor network system according to an embodiment of the present invention.

Referring to FIG. 2, a wireless sensor network system configures a network topology between a base station (BS) and a sensor node (SN) (S11). Here, the network topology may be implemented with a star topology that is directly connected between the base station (BS) and the sensor node (SN).

When the network topology is configured, the sensor node SN enters a sleep mode (S12). The sensor node SN waits for a control command transmitted from the base station (BS) in the sleep mode.

Then, the base station BS transmits an operation command to the sensor node SN according to the operation condition of the system (S13). In other words, the base station BS transmits an operation command packet to the sensor node SN, which instructs the start of operation.

Upon receiving the operation command transmitted from the base station BS, the sensor node SN awakes from the sleep mode and starts operation (S14).

Then, the sensor node SN transmits the sensor information to the base station BS (S15). Here, the sensor node SN transmits the sensor information sensed by the sensor in the form of a data packet. At this time, when receiving the data packet, the base station BS transmits an acknowledgment (ACK packet) to the corresponding sensor node SN.

Thereafter, the base station BS transmits an operation stop command to the sensor node SN according to the operation condition of the system (S16). For example, when the wireless sensor network system in the vehicle is to be stopped, the base station BS transmits an operation end command packet to the sensor node SN.

When the sensor node SN receives the operation stop command, the sensor node SN detects the remaining battery level of its own (S17).

The sensor node SN confirms whether the detected remaining battery level is equal to or less than a reference value (e.g., 30%) (S18). Here, the reference value may be applied and varied depending on the requirements of the system.

The sensor node SN transmits the node status information including its remaining battery level information to the base station (BS) in step S19 if the detected remaining battery level is less than the reference value. In other words, the sensor node SN recognizes itself as a problem node (PN) when the detected remaining battery level is less than the reference value. Here, the node status information may include battery remaining amount information and topology reconfiguration notification information indicating the topology reconfiguration execution. For example, a problem node (PN) whose remaining battery power is less than or equal to a reference value transmits a node status notification packet including battery remaining amount information and topology reconfiguration notification information to the base station (BS).

At this time, the base station (BS) transmits a response packet for receiving the node status information to the problem node (PN). Here, the base station BS provides the battery residual amount information for the problem node (PN) whose battery remaining amount is less than or equal to the reference value to the driver so that the driver can replace the battery of the problem node (PN).

Then, the sensor node SN reconfigures the existing topology based on the battery remaining amount and the LQI information of the neighboring nodes whose battery remaining amount is less than the reference value (S20).

In step S18, the sensor node SN enters the sleep mode when the battery remaining amount exceeds the reference value, and waits for a control command from the base station (S12).

3 is a flowchart illustrating a topology reconfiguration process shown in FIG.

First, the problem node (PN) searches for a neighbor node (NN) existing in the wireless sensor network (S21, S22). In other words, the problem node PN broadcasts an active scan request signal to search for a neighboring node NN (S21).

Upon receiving the active scan request signal, the neighboring node NN transmits its own LQI and battery remaining amount information in a beacon frame to the problem node PN (S22).

Upon receiving the beacon frame transmitted from the neighboring node NN, the problem node PN extracts the LQI and battery remaining amount information of the neighboring node NN included in the received beacon frame and stores the LQI and battery remaining amount information in the neighboring node table in step S23. The neighbor node table stores information on the LQI and the remaining battery level of each neighbor node NN and is referred to when selecting a neighbor node to be connected to the problem node PN.

The problem node (PN) compares the LQI of the neighbor nodes stored in the neighboring note table and the remaining battery level information, and selects a neighboring node (NN) to be connected (S24). At this time, the problem node (PN) considers the battery remaining amount of the neighboring nodes (NN) preferentially. Therefore, the problem node (PN) sets the weight of the battery remaining amount higher than the LQI. For example, the problem node (PN) sets the remaining battery level and the weight of LQI to 3 and 1.5, respectively.

The problem node (PN) computes the battery efficiency R of the neighboring node using Equation (1).

은 배터리 잔량을 100%로 환산된 값을 의미하고,

및

은 각각 배터리 잔량 및 LQI의 가중치를 의미한다. 가중치는 운전자에게 제공되는 시스템 및 서비스에 따라 가변적으로 변경 가능하다.Here, the remaining battery level

Means a value obtained by converting the remaining amount of the battery to 100%

And

Respectively indicate the remaining battery level and the weight of the LQI. The weights can be variably changed according to the system and the service provided to the driver.

In order to reconfigure the topology, the problem node (PN) selects a neighbor node (NN) having the largest battery efficiency R of the neighbor node as a neighbor node (NN) to be connected to the problem node (PN). Here, the selected neighbor node NN plays a role of relaying data between the problem node PN and the base station BS.

When the neighboring node NN to be connected is selected, the problem node PN transmits a connection request packet to the selected neighboring node NN (S26).

When the neighboring node NN receives the connection request packet from the problem node PN, it transmits a response packet to the problem node PN (S27). The problem node (PN) receives the connection response packet and reconfigures the topology by sending an acknowledgment packet to the selected neighboring node in response to the network connection between them.

4 is an exemplary diagram illustrating a reconstructed topology in accordance with an embodiment of the present invention.

As shown in Fig. 4, the problem node 3 arranged in front and the problem nodes 7, 8 disposed in the rear in which the remaining battery power is less than the reference value reconstitute the topology in order to use the batteries stored therein for a longer time more efficiently .

The problem node 3 reconfigures the topology by making a network connection with the neighboring node 2 having a battery efficiency R based on the remaining battery level information of the neighboring nodes 2 and 4 within the network range and the LQI.

The rearranged problem node 7 compares the remaining battery level information of the neighboring nodes 5, 6, and 8 within the network range with the battery efficiency R based on the LQI to determine whether the neighboring nodes 6, Reconfigure the topology. The rearranged problem node 8 compares the battery efficiency R on the basis of the remaining battery level information and the LQI of the neighboring nodes 5, 6 and 7 in the wireless sensor network, ) And reconfigures the topology.

In addition, when the topology is reconfigured, the problem node (PN) transmits battery remaining amount information remaining below the reference value to the connected neighbor node together with the sensor information so that the base station (BS) monitors the remaining battery level of the problem node .

0, BS: Base station
1 to 8, SN: sensor node
PN: Problem Node
NN: neighbor node

Claims (12)

Configuring a topology between a base station and sensor nodes constituting a wireless sensor network,
Detecting a remaining battery level when the sensor node receives a specific control command from the base station;
Checking whether the battery remaining amount detected by the sensor node is less than or equal to a reference value,
And if the remaining battery level is less than a reference value, the sensor node reconfigures the topology using the neighboring node. The method according to claim 1,
The topology configuration step includes:
And a star topology directly connected between the base station and each sensor node. The method according to claim 1,
The topology configuration step includes:
Further comprising: when the topology is configured, entering the sleep mode of the sensor node. The method according to claim 1,
The specific signal may be,
Wherein the stop command is an operation stop command transmitted from the base station. The method according to claim 1,
Wherein the topology reconstruction step comprises:
The sensor node transmitting node state information to the base station;
The sensor node searching for one or more neighbor nodes,
Selecting a neighboring node among the searched neighboring nodes based on a battery remaining amount and a link quality index of neighboring nodes searched by the sensor node;
And establishing a connection with the selected neighboring node by the sensor node. 6. The method of claim 5,
The node state information transmission step includes:
Transmitting the node status information including the battery remaining amount information and the topology reconfiguration notifying information if the detected remaining battery amount is less than a reference value;
And when the base station receives the node status information, notifying the driver of the insufficient remaining battery level of the sensor node that transmitted the node status information. 6. The method of claim 5,
Wherein the neighboring node searching step comprises:
The sensor node broadcasting an active scan request;
And transmitting a beacon frame to a neighboring node that has received the active scan request. 8. The method of claim 7,
The beacon frame transmission step includes:
Wherein the neighboring node having received the active scan request transmits its own battery remaining amount, link quality index, and sensor information in the beacon frame and transmits the beacon frame. 6. The method of claim 5,
Wherein the neighboring node selection step comprises:
Calculating a battery efficiency of each of the neighboring nodes searched by summing the battery remaining amount and the link quality index of the searched neighboring node;
Comparing the calculated battery efficiencies of the searched neighbor nodes;
And selecting the neighboring node with the highest battery efficiency among the searched neighboring nodes. 10. The method of claim 9,
Wherein the battery efficiency calculating step includes:
And calculating a weight of each of the battery remaining amount and the link quality index based on the weight of the battery remaining amount and the link quality index. 11. The method of claim 10,
Wherein the sensor node sets a higher weight to the remaining battery level than the link quality index. The method according to claim 1,
Further comprising the step of the sensor node transmitting remaining battery level information and sensor information to the neighboring node after the topology is reconfigured.

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