KR101184912B1 - Method and apparatus for providing communication in ground sensor network - Google Patents

Abstract

In order to operate a sensor network using magnetic field induction, the present invention proceeds research based on a model of collecting data from a sensor embedded in a building while moving a collector on the ground. Communication using magnetic field induction works at a short distance and does not spread far, so only sensor nodes located below the collector can participate in the communication, collecting data while moving the collector. However, since the transmission speed is not so large, the present invention intends to propose a communication technique capable of transmitting data efficiently as the collector moves. In addition, when a plurality of sensor nodes can communicate with the collector, we propose a communication protocol that can exchange data with the collector most efficiently.

Description

METHOD AND APPARATUS FOR PROVIDING COMMUNICATION IN GROUND SENSOR NETWORK}

TECHNICAL FIELD The present invention relates to a communication technology in an embedded sensor network, and more particularly, to a communication method and apparatus in an embedded sensor network using magnetic field induction.

The present invention is derived from a study conducted as part of the IT industrial source technology development project of the Ministry of Knowledge Economy and Korea Institute of Industrial Technology Evaluation and Management [2008-F-044-02, Intelligent construction IT convergence to improve electromagnetic wave, sound and building environment New technology development].

There is an active research on the communication method using the building sensor network. For example, the embedded sensor node is designed to collect data through wireless transmission of one hop as shown in FIG. do.

However, such a sensor node can only be exposed to the ground in order to avoid the communication obstacles caused by the landfill, there may be a problem in terms of the installation of the sensor and the stability of the sensor node.

To solve this problem, all parts of the sensor must be embedded in the building. Therefore, researches for constructing a building sensor network by connecting sensors to a building by wires have also been conducted. However, these methods also have problems in installation, which causes problems in actual use.

Thus, research on wireless building sensor networks has begun. Wireless building sensor network technology is a system that allows sensor nodes to deliver embedded and sensed data without connecting any wires. However, many challenges remain in these wireless building sensor networks.

First, the power consumption problem can be mentioned. Because wireless sensor nodes are embedded in buildings, it is difficult to supply power in the middle or to install and replace additional sensor terminals. Therefore, it is necessary to enable semi-permanent use. In general, when communicating using only a battery, it can no longer be used after a certain time. In the existing wireless sensor network, studies on semi-permanent sensor nodes through solar energy charging using solar cells have been applied.

However, such solar energy has many limitations in being applied to building sensor nodes. Antennas are also a big problem on building wireless sensor networks. For example, because antennas exist in walls, antennas must be designed to take into account the effects of reflections from the building materials surrounding the sensor. Since it does not pass well, it should try to transmit at low frequency and accordingly, the size of the antenna must be increased.

The solution to this problem is to apply a communication technology using magnetic field induction. Using magnetic field induction, it is possible to supply power by using magnetic field first, which can solve the power problem of the sensor node. Since magnetic field is hardly influenced by the medium, if only coils of appropriate size are wound, communication in buildings You can do it.

In the magnetic field communication, as shown in FIG. 2, a terminal of a transmitting and receiving terminal transmits and receives a signal through magnetic field induction by changing a magnetic field by a change in current flow of an antenna coil.

Magnetic field wireless communication is currently used in RFID. In the near field RFID method, RFID readers can generate a magnetic field, and when RFID tags near the reader, the magnetic field is used to charge power to change the magnetic field. The data can be transmitted to the reader.

Such magnetic field induction RFID technology has been established and developed as a standard, and recently has been developed by a group called NFC (near field communication).

NFC supports up to p2p mode, aims to support speeds up to 424kbit / s using the 13.56MHz frequency band and up to 1Mbit / s in the future.

However, there is a problem in applying the magnetic field induction communication which is utilized in such RFID to the buried sensor directly.

First, it's a matter of mastery. The communication range of NFC-based NFC is only a few centimeters. Therefore, there is a need for a study on magnetic field induction communication having a longer communication distance.

In the present invention, a model in which a collector collects data may be considered. In such a form, a plurality of sensor nodes may attempt to transmit data to the collector. However, since RFID-based communication methods such as NFC lack the definition of such multiple access, it may be necessary to study the multiple access that meets the magnetic field induction characteristics.

In order to solve the problem of the building wireless sensor network, in the embodiment of the present invention, a magnetic field induction scheme may be used.

By using the magnetic field induction method, the building wireless sensors can be less environmentally affected, and the power problem of the building wireless sensor network can be solved through the power transmission using the magnetic field induction. As the current communication method using magnetic field induction is only near field RFID, research on more various sensor network technologies using magnetic field communication is needed.

In the embodiment of the present invention for the operation of the sensor network using the magnetic field induction, it is possible to collect data from the sensor embedded in the building while moving the collector on the ground.

Communication using magnetic field induction works at close range and does not spread far, so only sensor nodes located below the collector can participate in the communication and collect data as the collector moves.

However, since the transmission speed is not very large, an embodiment of the present invention proposes a technique capable of transmitting data efficiently as the collector moves.

In addition, when a plurality of sensor nodes can communicate with the collector, we propose a technology that can exchange data with the collector most efficiently.

According to a communication method in an embedded sensor network for solving the problem of the present invention, a polling message (polling) from the collector (collector) moving on the ground or building surface, the sensor node embedded in the ground or building message), and the sensor node random access to the collector in response to the polling message.

Here, the random access may include a process of determining whether the sensor node is redundantly transmitted according to whether or not the collector node responds by random number of collected data according to random access of the sensor node.

The determining of whether or not the redundant transmission may include: when the collection data of the sensor node reacts by the random number, not transmitting the response collection data; and wherein the collection data of the sensor node does not react by the random number. Otherwise, the collector may randomly access the unreacted collected data.

In addition, the polling message may be transmitted to the sensor node by a magnetic field induction scheme.

In addition, the sensor node may be charged by the magnetic field induction method.

In addition, the random access process may include accessing with a transmission probability based on an Aloha protocol.

In addition, the collector may move in N slot times, but the transmission probability may increase for each slot time.

According to a communication device in an embedded sensor network for solving the problems of the present invention, an aloha corresponding to a collector generating a polling message while moving on the ground or the surface of a building, receiving the polling message, and responding to the polling message received. At least one sensor node embedded in the ground or building, which randomly accesses the collector with a protocol-based transmission probability.

Here, the polling message may be characterized in that the magnetic field induction method.

The collector may determine whether the data is redundantly transmitted according to a response of a random number of data collected from the at least one sensor node.

According to the embodiment of the present invention, by using the magnetic field induction method, the building wireless sensors are less environmentally affected, it is possible to solve the power problem of the building wireless sensor network through the power transfer using the magnetic field induction. In addition, according to an embodiment of the present invention, it is possible to efficiently transmit data in accordance with the movement of the collector, it is possible to exchange data with the collector most efficiently when a plurality of sensor nodes can communicate with the collector.

1 is an exemplary view of a general embedded sensor;
2 illustrates a general electromagnetic induction principle,
3 is a diagram illustrating a data transmission process according to a moving collector according to an embodiment of the present invention;
4 exemplarily illustrates a communication principle in an embedded sensor network using magnetic field induction according to an embodiment of the present invention;
FIG. 5 is a diagram for explaining a communication principle when a collector moves on a buried sensor according to an embodiment of the present invention; FIG.
6 is a graph illustrating the number of transmission success sensor nodes according to a dwell time of a collector according to an embodiment of the present invention;
7 is a graph illustrating the number of successful transmissions according to the number of sensors existing under the collector according to an embodiment of the present invention.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. To fully disclose the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. Like numbers refer to like elements throughout.

In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. The following terms are defined in consideration of the functions in the embodiments of the present invention, which may vary depending on the intention of the user, the intention or the custom of the operator. Therefore, the definition should be based on the contents throughout this specification.

Each block of the accompanying block diagrams and combinations of steps of the flowchart may be performed by computer program instructions. These computer program instructions may be loaded into a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus so that the instructions, which may be executed by a processor of a computer or other programmable data processing apparatus, And means for performing the functions described in each step are created. These computer program instructions may be stored in a computer usable or computer readable memory that can be directed to a computer or other programmable data processing equipment to implement functionality in a particular manner, and thus the computer usable or computer readable memory. It is also possible for the instructions stored in to produce an article of manufacture containing instruction means for performing the functions described in each block or flowchart of each step of the block diagram. Computer program instructions may also be mounted on a computer or other programmable data processing equipment, such that a series of operating steps may be performed on the computer or other programmable data processing equipment to create a computer-implemented process to create a computer or other programmable data. Instructions that perform processing equipment may also provide steps for performing the functions described in each block of the block diagram and in each step of the flowchart.

Also, each block or each step may represent a module, segment, or portion of code that includes one or more executable instructions for executing the specified logical function (s). It should also be noted that in some alternative embodiments the functions noted in the blocks or steps may occur out of order. For example, two blocks or steps shown in succession may in fact be performed substantially concurrently, or the blocks or steps may sometimes be performed in reverse order according to the corresponding function.

In the present invention, a model in which a collector collects data may be considered. In such a form, a plurality of sensor nodes may attempt to transmit data to the collector. However, since RFID-based communication methods such as NFC lack the definition of such multiple access, it may be necessary to study the multiple access that meets the magnetic field induction characteristics.

In order to solve the problem of the building wireless sensor network, in the embodiment of the present invention, a magnetic field induction scheme may be used.

By using the magnetic field induction method, the building wireless sensors can be less environmentally affected, and the power problem of the building wireless sensor network can be solved through the power transmission using the magnetic field induction. As the current communication method using magnetic field induction is only near field RFID, research on more various sensor network technologies using magnetic field communication is needed.

In the embodiment of the present invention for the operation of the sensor network using the magnetic field induction, it is possible to collect data from the sensor embedded in the building while moving the collector on the ground.

Communication using magnetic field induction works at close range and does not spread far, so only sensor nodes located below the collector can participate in the communication and collect data as the collector moves.

However, since the transmission speed is not very large, an embodiment of the present invention proposes a technique capable of transmitting data efficiently as the collector moves.

In addition, when a plurality of sensor nodes can communicate with the collector, we propose a technology that can exchange data with the collector most efficiently.

First, in an embodiment of the present invention, the MAC protocol for an aloha-based building wireless sensor network may be applied.

In an embodiment of the present invention, a sensor network topology using a collector may be applied, where the collector may be fixed or mobile.

Since magnetic field induction does not have a propagation characteristic over a long distance, it is desirable to implement communication with sensors located around a moving collector.

If it is assumed that the user can collect data from all the sensors and grasp the information of the sensors embedded in the building, the user who collects the data through the collector is difficult to pinpoint the location of the embedded sensor. Since we don't know if we collected data, we need to collect information several times to collect data from all sensors.

FIG. 3 is a diagram illustrating a snapshot of a transmission state of a sensor network that may occur when such a building sensor network operates.

In FIG. 3, circles represent sensor nodes 202 that have not been transmitted yet, and asterisks may mean sensor nodes 204 that have completed data transmission.

In such a state, only the sensor nodes 202 that do not transmit data may react to reduce the probability of collision, and duplicate data may disappear to collect all data in a shorter time.

Some problems can occur if the sensor node that has simply reacted is not retransmitted. If the collector 100 wants to read the data of the sensor node again from the beginning, a problem may occur in which data cannot be collected when the sensor node once transmitted does not react again.

In an embodiment of the present invention, in order to solve such a problem, a method of generating a random number at the time of data collection is proposed.

By the random number, the sensor nodes can determine whether the data collection has been previously responded to, and can transmit only the data collection that did not respond.

Given this one-time response, you have to decide which multiple access scheme to use. Since the collector 100 is fixed or continuously moving and does not know which sensor nodes are capable of communicating below, a connection method suitable for this characteristic should be proposed.

The most basic method that can be considered is that when the collector 100 polls, the sensor nodes that receive the message randomly access based on the Aloha protocol. It can be implemented to try.

For example, as shown in FIG. 4, the collector 100 transmits a polling message to the sensor node 200 below while being fixed or moving.

Since this message uses magnetic field induction, the sensor node 200 located below can charge its own power while receiving a polling message.

The sensor node 200 receiving the polling message may attempt to transmit with a transmission probability p based on the Aloha protocol.

However, since the terminal which has successfully transmitted data does not attempt transmission again, a more efficient transmission scheme may be considered.

So far, the algorithm has been proposed and performance has been analyzed for a simple situation. For example, assuming that n sensor nodes 200 are listed in a line as shown in FIG. 5, and the collector 200 passes through N slot times for the following three methods, You can compare the performance.

1) Aloha protocol with probability p = 1 / n

When n sensor nodes 200 attempt to transmit with a probability of p, the transmission success probability may be expressed by Equation 1 below.

Therefore, when there are n sensor nodes 200, the transmission probability p that obtains the highest success probability may be 1 / n.

Likewise, the transmission success probability when n-1 sensors left after one sensor succeeds in transmission with a transmission probability p may be expressed by Equation 2 below.

들을 이용하여 상태 전이 매트릭스(state transition matrix)를 구할 수 있다.If we define the number of sensor nodes left as state, we get the probability of success

The state transition matrix can be obtained using these methods.

라고 가정할 때 상태 전이 매트릭스 Pt는 다음 [수학식 3]과 같이 표현될 수 있다.The probability of transitioning from state i to state j

It is assumed that the state transition matrix Pt can be expressed as Equation 3 below.

에 대하여

,

가 되며

인 경우에는

이 되고 나머지 모든 경우는

가 된다.These values

about

,

Becomes

If is

And everything else

.

In addition, the probability of staying in each state after N slots has passed may be expressed as a result vector v as shown in Equation 4 below.

의 계산을 통하여 구할 수 있게 된다.In the embodiment of the present invention using the result vector v, the expected value of the number of successful transmissions in N slots is obtained.

It can be obtained by calculating.

2) optimal aloha protocol

As described above, in a situation where n terminals exist, the most optimal transmission probability may be 1 / n. If all the terminals can grasp the number of sensor nodes that want to communicate under the current collector 100, each sensor node can calculate the transmission probability as shown in [Equation 5] using the number.

와

를 구하게 되면

의 계산을 통하여 N 번의 슬롯 동안 성공한 전송 횟수의 기대값을 구할 수 있게 된다.In the same way as above using the transmission probability as shown in [Equation 5]

Wow

If you find

Through the calculation of, the expected value of the number of successful transmissions in N slots can be obtained.

3) a communication method according to an embodiment of the present invention

It is difficult to use the optimal method when it is difficult for the sensor terminals to accurately determine the number of sensors present.

In an embodiment of the present invention, a technique of increasing a transmission probability in every slot may be applied.

Considering that there is a transmission success probability every frame and the number of expected sensor nodes can be reduced, the communication method according to the embodiment of the present invention can increase efficiency.

In an embodiment of the present invention, the transmission probability may be linearly increased.

를 i 번째 슬롯의 전송 확률이라고 할 때 다음 [수학식 6]와 같은 전송 확률을 가정할 수 있다.

When we denote the transmission probability of the i-th slot, we can assume a transmission probability as shown in Equation 6 below.

를 i번째 슬롯에서 상태 l에서 상태 k로 천이 되는 확률이라고 정의하면, 해당하는 확률 값들은

에 대하여 다음 [수학식 7]와 같이 정의될 수 있다.Likewise

Is defined as the probability of transitioning from state l to state k in the i th slot, the corresponding probability values

It may be defined as in Equation 7 below.

인 경우에는

이 되고 나머지 모든 경우는

가 된다.

If is

And everything else

.

In this case, the transition matrix per slot may be differently represented as in [Equation 8].

In addition, v may be represented by the following [Equation 9].

계산을 통하여 N번의 슬롯 동안 전송 성공한 기대 값을 구할 수 있다.therefore,

Through the calculation, it is possible to obtain the expected value of successful transmission during N slots.

6 assumes a situation in which the number of sensors existing under the collector is fixed to 3, and looks at the result while changing the time that the collector is present on the sensor.

As the length of time that the collector stays on the sensor node increases, the opportunity for sensor nodes to transmit their data increases, so we can see that the expected number of successful sensor nodes is approaching three.

According to the embodiment of the present invention, it can be seen that the smaller than the optimization state, but has a better performance than the conventional method. This is because the communication method according to the embodiment of the present invention increases the probability of transmission over time, and is larger than the case of simply fixing the probability of transmission because the number of remaining untransmitted sensor nodes decreases over time. This may mean that the transmission will be successful.

FIG. 7 illustrates the performance by changing the number of sensor nodes existing under the collector while fixing the dwell time of the collector to 10 frames.

It can be seen that the performance of the sensor node is higher than that of the conventional communication method according to the change of the number of sensor nodes. However, as the number of sensor nodes increases, the performance improves and then falls again. This is because as the number of sensor nodes increases, the amount of sensors to be transmitted increases, but the probability of collision occurs.

As described above, according to the embodiment of the present invention, by using the magnetic field induction method, the building wireless sensors are less environmentally affected, so that the power problem of the building wireless sensor network can be solved through the power transmission using the magnetic field induction. It is an implementation. In addition, according to an embodiment of the present invention, it is possible to efficiently transmit data in accordance with the movement of the collector, it is implemented so that a plurality of sensor nodes can exchange data with the collector most efficiently when it can communicate with the collector. .

100: collector
200: sensor node

Claims (10)

delete Transmitting a polling message from a collector moving on the ground or building surface to a sensor node embedded in the ground or building;
And randomly accessing the sensor node to the collector in response to the polling message.
The random access process,
And determining, by the collector, whether or not the sensor node is redundantly transmitted according to whether or not a response of the collected data according to random access of the sensor node is caused by a random number.
Communication method in embedded sensor network.
The method of claim 2,
The process of determining whether the duplicate transmission,
Not transmitting the collected collected data when the collected data of the sensor node reacts by the random number;
If the collected data of the sensor node does not react by the random number, the collector randomly accessing the unreacted collected data;
Communication method in embedded sensor network.
delete delete The method of claim 2,
The random access may include accessing at a transmission probability based on an Aloha protocol.
Communication method in embedded sensor network.
The method of claim 2,
The collector moves to N slot times, but the transmission probability increases every N slot times.
Communication method in embedded sensor network.
Collectors that generate polling messages while traveling on the ground or on the surface of a building,
At least one sensor node embedded in the ground or building that receives the polling message and randomly accesses the collector with an Aloha protocol based transmission probability in response to the polling message being received.
Communication device in embedded sensor network.
The method of claim 8,
The polling message is characterized in that the magnetic field induction method
Communication device in embedded sensor network.
The method of claim 8,
The collector determines whether the data is redundantly transmitted according to a response of a random number of data collected from the at least one sensor node.
Communication device in embedded sensor network.

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