KR20090093543A - Radio frequency sensor network system and data communication method thereof - Google Patents

Abstract

A radio sensor network system and a data communication method of the system for accurately sensing the location of the user in intelligent home network system are provided to distribute ratio power efficiently and manage the network failure situation in network error situation. A blind node of a user transmits data packet about the location of the user to a first node(121). The first node transmits the data packet to the second node(122). The second node returns the response packet toward the reception of data packet to the first node. The received data packet is transmitted to a third node(123).

Description

Wireless Sensor Network System and Data Communication Method {RADIO FREQUENCY SENSOR NETWORK SYSTEM AND DATA COMMUNICATION METHOD THEREOF}

The present invention relates to a wireless sensor network system and a data communication method of the system.

The wireless sensor network can be applied to various fields such as home network, environment monitoring, factory management, healthcare, military, and the like. Thanks to this, it has continuously developed into a small, low cost, low power wireless sensor.

Meanwhile, the home network system enables intelligent communication through network matching between a home network and an external communication network, thereby sharing indoor information resources such as a home or an office and maximizing the utility of home devices constituting a home network. Means.

The home network system has evolved from a wired base to a wireless base of a ubiquitous environment as the wireless sensor network develops, and has developed to provide a level of intelligent services differentiated by users at the level of simply controlling home devices. Doing.

For the intelligent home network system, a technology for detecting a location of an object or a user using a wireless sensor network is required. After detecting the user's location, the system can automatically control each home device based on the user's location, or can monitor the user's movement and movement at a remote location in real time and use it as various data.

However, if the user wants to detect the location of the user based on the wireless infrastructure, network disconnection situations frequently occur due to factors such as indoor conditions or poor wireless environment, and active measures for improving the network disconnection situation are insufficient. There is a problem that it is difficult to detect the effective user location.

In addition, even when the wireless sensor network is to be applied to various other fields, network disconnection and communication failure caused by the wireless environment make it difficult to smoothly communicate data and deteriorate the reliability of the system.

Accordingly, an object of the present invention is to provide a wireless sensor network system and a data communication method of the system capable of actively coping with a network failure situation and efficiently distributing wireless power.

Another technical problem to be achieved by the present invention is to provide a wireless sensor network system and a data communication method of the system that can be applied to an intelligent home network system to accurately detect a user's location in a wireless environment.

Technical problems to be achieved by the present invention are not limited to the above-mentioned technical problems, and other technical problems not mentioned above may be clearly understood by those skilled in the art from the following description. There will be.

Wireless sensor network system according to the present invention for achieving the above object, the blind node carried by the user; And forwarding the data packet received from the blind node along the default path along the default path, and in case of a network failure, changing the default path to an alternative path to forward the data packet again through the alternative path. Contains a reference node.

On the other hand, the data communication method of the wireless sensor network system, for each of the plurality of reference nodes having a wireless sensor, the step of setting a default path and at least one alternative path for data transmission for each reference node; Receiving, by any child node which is one of the plurality of reference nodes, a data packet transmitted from a blind node carried by a user and forwarding the data packet to a parent node corresponding to a default path; And in the event of a network failure, the child node changing the default path to an alternate path and forwarding the data packet to another parent node again.

The wireless sensor network system and the data communication method thereof according to the present invention made as described above can actively cope with a network failure situation and can efficiently distribute wireless power.

In addition, the wireless sensor network system and the data communication method of the system according to the present invention, supports an intelligent home network system that can accurately detect the location of the user in a wireless environment.

1 is a partial configuration diagram of a wireless sensor network system according to an embodiment of the present invention.

2 is a data flow diagram illustrating a data communication method of a wireless sensor network system according to an embodiment of the present invention.

FIG. 3 is a diagram for explaining the routing path of FIG. 2.

4 is a table for exemplarily illustrating a change in wireless power of FIG. 2.

*** Explanation of symbols for the main parts of the drawing ***

110: blind node 120: reference node

130: base station

Hereinafter, a wireless sensor network system and a data communication method of the system according to a preferred embodiment of the present invention will be described in detail with reference to FIGS. 1 to 4.

The wireless sensor network system and data communication method of the system to be described later can be applied to various fields such as home network, environmental monitoring, factory management, healthcare, transportation, etc. A preferred embodiment of the present invention will be described.

1 is a block diagram of a wireless sensor network system according to an embodiment of the present invention, and implements a platform for indoor location recognition.

Referring to FIG. 1, in the wireless sensor network system according to an exemplary embodiment of the present invention, a blind node 110 and a plurality of reference nodes 121 to 126 are hereinafter referred to as unnecessary. 120 collectively), and a base station 130.

Here, the wireless sensor network including the blind node 110, the plurality of reference nodes 120, the base station 130 may be constructed in accordance with the standard of IEEE802.15.4.

The user carries the blind node 110 for position estimation, and the blind node 110 generates a data packet for the user position through triangulation based on Radio Signal Strength Information (RSSI).

According to the RSSI-based triangulation method, the blind node 110 emits a broadcast signal to measure RSSI values of surrounding reference nodes. That is, the blind node 110 emits a broadcast signal to adjacent reference nodes, and receives a signal including its node ID, current position (X, Y coordinate), RSSI value, etc. from the corresponding reference nodes. do. Thereafter, the blind node 110 selects a reference node having the highest RSSI value as an initial transmission node of the routing path and transmits a data packet for a user location to the reference node.

If the reference node having the highest RSSI value corresponding to the broadcast signal sent to neighboring reference nodes is selected as the initial transmission node, network disconnection caused by the communication distance can be improved.

In FIG. 1, RSSI values of the first node 121, the second node 122, the fifth node 125, and the sixth node 126 are illustrated as -43 dBm, -49 dBm, -57 dBm, and -63 dBm, respectively. The first node 121 having the highest RSSI value is selected as an initial transmitting node and receives a data packet from the blind node 110.

The reference node 120 has a wireless sensor installed at an appropriate range (eg, installed in each room in one building), and one reference node 120 transmits a data packet to another reference node 120 and then The network failure situation is determined according to whether a response packet is received. The range in which the wireless sensors are installed is within one hop from which radio signals can reach each other.

In addition, by applying a wireless sensor that senses and collects environmental information such as temperature, humidity, and illumination for each reference node 120, it is possible to provide more ubiquitous services.

Each reference node 120 stores a default path used as a routing path of a data packet and one or more alternative paths in advance. A user's data packet received from the blind node 110 to any reference node 120 is forwarded to another reference node 120 according to the basic path of each reference node 120.

If a network failure occurs during the forwarding process, the reference node 120 that transmits the data packet changes the routing path to the alternative path and forwards the data packet again through the alternative path.

Since the amount of traffic required to perform location estimation increases exponentially with the number of nodes, the location estimation of the system as shown in FIG. 1 is efficient to use in a relatively small network and a limited number of nodes.

Meanwhile, when each reference node 120 forwards a data packet to another reference node 120, the wireless power may be actively changed according to a situation.

For example, when the distance from the parent node to forward the packet is more than two hops, the reference node 120, which is a child node that forwards the packet, forwards the data packet by actively changing the wireless power to a maximum value. Alternatively, by inspecting the battery state of the node itself, when the battery voltage is less than the reference voltage, the child node actively lowers the wireless power and forwards the data packet, thereby enabling efficient data transmission.

The wireless sensor constituting each reference node 120 often aims for small size, low cost, and low power, and in the case of a low power, low cost system in which the wireless sensor is battery operated, the space where the wireless sensor network is disposed is physically limited. It can be a poor and variable place.

In order to establish a low power and strong networking in such an environment, the system according to an embodiment of the present invention may vary routing paths according to a situation so as to actively cope with a situation causing communication failure, and according to a communication distance or a battery condition. Actively control wireless power.

Each reference node 120 may additionally perform an operation for preventing a data packet from being delivered to the base station 130 due to a looping phenomenon. For example, when the hop count of the data packet is greater than or equal to a predetermined value, the reference node 120 as a child node determines the data packet as a looping packet and discards it, or excludes the parent node forwarding the data packet from the routing path. Packet transmission rate can be increased.

Base station 130 is a radio transceiver (RF Transceiver) that is the destination that the data packet transmitted from the blind node 110 finally arrives, the remote server by receiving the data packet through the reference node 120 in the routing path Acts as a gateway to pass to (not shown).

The remote server (not shown) may receive the user's data packet through the base station 130 to check the current position of the blind node 110 in real time, and collect data from the plurality of reference nodes 120 to collect the data. The reference node 120 will be managed.

In addition, the remote server (not shown) controls the reference nodes 120 to be wireless to control the wireless power (RF power), packet interval (Sleep mode / Wake Up mode), routing path (Routing) of the wireless sensor. Path), an end device, and the like, and thus, the reference nodes 120 widely distributed may be more easily and efficiently managed.

The operation of the system shown in FIG. 1 will be briefly described as follows. For convenience of explanation, it is assumed that a network disconnection occurs in the third node 123 belonging to the default path, and an alternate path from the second node 122 to the fourth node 124 is selected to transmit a packet. .

As described above, the blind node 110 carried by the user transmits a data packet of the user's location measured through RSSI-based triangulation to the first node 121 having the highest RSSI value.

The first node 121 selects a default path using table-type static forwarding and transmits a data packet to the second node 122 according to the default path. The second node 122 returns a response packet to the reception of the data packet to the first node 121 and transmits the received data packet to the third node 123 along the basic path.

When transmitting a data packet, the first node 121 and the second node 122 determine whether the data transmission is successful by receiving an ACK packet.

If the second node 122 does not receive the response packet more than a certain number of times (eg, three times) from the third node 123 for a predetermined time, the second node 122 determines that the network has failed, and determines the routing path. Actively changing from the primary path to the alternate path forwards the data packet back to the fourth node 124. One or more alternate paths are preset in the second node 122 in a static manner, and when detecting a network failure, the second node 122 sequentially selects and applies the alternate paths having higher priority.

The fourth node 124 forwards the received data packet to the base station 130.

When transmitting a data packet, the reference node 120 serving as a child node may actively change wireless power according to a situation. For example, when a routing path is established from the second node 122 to the fourth node 124 so that the hop count distance becomes two or more, the second node 122 changes the wireless power to the maximum value and forwards the data packet. do. Hop count is a routing metric used to measure the distance between the originating node and the receiving node.

In comparison, when the distance between nodes that communicates without network failure is 1 hop, average wireless power is used.

In addition, when the data packet is transmitted, if the battery of the reference node 120 is below the recommended level, the reference node 120 serving as a child node forwards the data packet by changing the wireless power to a minimum value.

2 is a data flow diagram illustrating a data communication method of a wireless sensor network system according to an embodiment of the present invention, illustrating a data communication method performed in the system of FIG. 1. As in FIG. 1, it is assumed that the first node 121 is an initial transmitting node and the routing path is changed from the second node 122 to the fourth node 124 due to the failure of the third node 123. do.

First, in step S110, for each of the plurality of reference nodes 120 in which the wireless sensor is installed, a basic path for data transmission and one or more alternative paths are set for each reference node 120.

Next, in steps S120 and S130, a data packet indicating a location of a user is transmitted through a routing path of a wireless sensor network composed of a plurality of reference nodes 120.

The routing path of step S120 is a default path, and when the reference node 120 in the default path detects a network failure situation, the process proceeds to step S130 to change the routing path to an alternative path.

Any reference node 120 that becomes a child node receives a data packet transmitted from the blind node 110 carried by the user, and then checks a previously stored default path, and according to the default path, the parent node ( The data packet is forwarded to another reference node 120 which is a parent node.

Looking at the step S120 in detail.

In steps S121 and S122, the blind node 110 selects the first node 121 nearest to the neighboring reference nodes 120 as an initial transmission node, and informs the user location of the selected initial transmission node. Send the packet.

When selecting the initial transmission node, the blind node 110 selects the reference node 120 having the highest Radio Signal Strength Information (RSSI) value as the initial transmission node by applying an RSSI-based triangulation method.

Thereafter, in steps S123 to S127, data packets are forwarded sequentially from the first node 121, which is the initial transmitting node, through the reference nodes 122 in the default path, and this process continues unless a network failure is detected. do.

In operation S130, the reference node 120 that detects the network failure changes the routing path to an alternative path and transmits a data packet to a parent node different from the previous process.

First, in step S131, the second node 122 detects a network failure through whether or not a response packet is received from the third node 123 that delivered the data packet. For example, if a response packet is not received even after 40 ms of transmitting the data packet, the process of forwarding the data packet to the third node 123 is repeated three times. If the response packet is not transmitted despite three or more repetitive attempts, the second node 122 proceeds to step S132, and in steps S132 and S133, the fourth node 124 changes the routing path to an alternate path. Forwards the data packet.

In step S134, the fourth node 124 transmits the response packet to the second node 122 to inform that the data packet was successfully delivered.

When one reference node 120 serving as a child node transmits a data packet with another reference node 120 as a parent node, the child node actively transmits wireless power according to the distance between itself and the parent node that forwards the data packet. Can be increased to increase communication efficiency and reduce power.

That is, as in steps S133 and S134, when the distance between the child node and the parent node is more than two hops, the child node transmits a data packet by increasing wireless power. In addition, the child node checks its own battery state and transmits data packets by lowering wireless power when the battery voltage is less than the reference voltage as a result of the test.

3 is a diagram for exemplarily describing the routing path of FIG. 2. FIG. 4 is a table for exemplarily illustrating a change in wireless power of FIG. 2 and illustrates wireless power that varies according to a situation.

As shown in FIG. 4, each reference node 120 is configured with a basic path a and three alternative paths b, c, and d in a static manner. Preconfiguring and storing alternative paths in a static manner can be more efficient in terms of power, time, and load, compared to actively searching for the situation.

The reference node 120, which is a child node, forwards the data packet to the parent node, and if the response packet is not received, attempts to forward the data packet a predetermined number of times (for example, three times).

In spite of repeated attempts, if no response packet is received from the parent node more than a certain number of times, the child node determines that the parent node is down, and actively changes the parent node to the next predetermined alternate path. Forward data packets to the parent node.

Referring to the table of FIG. 4, when the parent node is at a distance of one hop capable of direct communication with average wireless power, the child node uses 15 levels of wireless voltages consuming 12.5 mA of current, If it is a distance, it forwards the packet by consuming 17.4mA of current, the maximum transmission of wireless power.

By flexibly varying the wireless power along the routing path, network disconnection caused by one-hop communication distance constraint (for example, when using a network of a star topology model) can be improved, resulting in a more reliable and stable system.

Applying this to FIG. 3 is as follows.

Indoors, each room is equipped with a wireless sensor as a reference node 120, the distance between one hop is set so that the signal can be reached with a wireless power of 15 levels of average value, each reference node 120 in a static manner For each wireless sensor, the default route and three alternate routes are configured as routing paths.

In (a) any reference node 120 transmits the data packet to the next hop reference node 120 and checks if a response packet arrives after a certain time (eg 40 ms). If a response packet is not received from a parent node while sending a data packet a predetermined number of times (eg, three times) along the routing path designated as the default path, the child node determines that the next hop parent node is down and the routing path is down. Change to the first alternate path defined as (b).

As with the primary route, if the first alternate route does not receive a response packet more than a certain number of times (eg, three times) from another parent node of the next hop, the child node determines that the parent node is down and the second alternate route of (c) Will be used.

Up to the second alternate path, 15 levels of 12.5 mA of wireless power are used to transmit the data packet. In this configuration, even if an abnormality occurs in the reference node 120 disposed in each room of the room, all data packets can be transmitted to the base station 130 using a predetermined alternative route actively.

(d) is the third alternative path, and when the second alternative path of (c) is down, the reference node 120 at a distance of two hops is set as the parent node of the alternative path. In the case of (d), the wireless power is set to 31 levels, which is the maximum value, to enable wireless communication at a distance of two hops apart.

As described above, each reference node 120 detects that the current routing path is a network failure situation when the response packet is not received using the response packet for a predetermined time or a predetermined number of times. In addition, by forwarding data packets by quickly and actively changing routing paths to static alternative paths of a predetermined table type, the reference node 120 having limited system resources can significantly reduce network topology reconfiguration time with only a small amount of memory. .

On the other hand, when the reference node 120 uses an alternate path, a data packet may be looped without finding the base station 130 and thus packet transmission may be impossible. In this case, if the reference node 120 that has already received the data packet is excluded even if it is included in the alternate path and another routing path can be used, this looping phenomenon can be prevented.

In addition, it is possible to cope more actively with the environment such as the off or failure of the wireless sensor through the use of alternative paths and several additional configurations.

For example, when the hop count received from the reference node 120 is equal to or greater than a predetermined value (for example, 20), it is determined that the corresponding data packet is a looping packet, and discards the packet by adding sequence data to the data packet. By checking, the configuration or the like for confirming the reception rate of the packet can be utilized.

In order to prevent network looping during forwarding, if the hop count of the forwarding packet is greater than or equal to a predetermined value (for example, 20) in a small network, the reference node 120 determines that the looping phenomenon and stops forwarding, and forwards the packet. Notify on the side.

In addition, even when the node ID of the node receiving the packet is included in the alternative path, the failure situation can be prevented by selecting another alternative path without returning the packet again.

The method of estimating the location of a user by applying the above-described data communication method in an integrated or selective manner is more efficient than the method of simply applying a star topology model or an Ad_hoc routing system to a wireless sensor network.

When data packets are forwarded to a server using a conventional star topology model, network disconnection occurs frequently due to traffic bias or limited distance between nodes of one hop.

In the case of the Ad_hoc routing system, the child node consumes high system resources in a limited resource radio sensor in order to determine another parent node according to a situation (for example, when a user moves during location tracking). Therefore, it takes too long to create an initial network topology and to change the topology in the event of a network failure, and the system battery is inefficiently consumed by the use of passive wireless power.

On the other hand, according to the preferred embodiment of the present invention, it is possible to determine the optimal network path in a short time because the topology creation time and change time are small, and loop counting can be prevented by checking the hop count, and actively depending on the situation It consumes a battery and can transmit data efficiently. This advantage can be more powerful in smaller networks that require faster installation times and reliability.

Although embodiments of the present invention have been described above with reference to the accompanying drawings, those skilled in the art to which the present invention pertains may implement the present invention in other specific forms without changing the technical spirit or essential features thereof. I can understand that.

That is, the present invention can be applied to various fields such as environmental monitoring, factory management, healthcare, transportation, military, medical care, as well as the location tracking system of the home network described above as an embodiment.

Therefore, since the embodiments described above are provided to completely inform the scope of the invention to those skilled in the art, it should be understood that they are exemplary in all respects and not limited. The invention is only defined by the scope of the claims.

Claims (12)

Blind node; And A plurality of references including a wireless sensor to forward the data packet received from the blind node along the default path, when the network failure occurs, by changing the default path to an alternative path to forward the data packet again through the alternative path Node Wireless sensor network system comprising a. The method of claim 1, wherein each of the plurality of reference nodes, A default path and one or more alternative paths used as routing paths of the data packets are preset and stored Wireless sensor network system characterized in that. The method of claim 1, wherein the blind node, It emits a broadcast signal to measure RSSI (Radio Signal Strength Information) values of neighboring reference nodes, selects a reference node having the highest RSSI value as an initial transmitting node, and transmits the data packet to the initial transmitting node. To do Wireless sensor network system characterized in that. The method of claim 1, wherein each of the plurality of reference nodes, After transmitting the data packet to another reference node, determining a network failure condition according to whether a response packet is received Wireless sensor network system characterized in that. The method of claim 1, wherein each of the plurality of reference nodes, Actively varying wireless power according to circumstances when forwarding the data packet Wireless sensor network system characterized in that. The method of claim 1, wherein each of the plurality of reference nodes, If the hop count of the data packet is greater than or equal to a predetermined value, determine that the data packet is a looping packet and discard it, or exclude the parent node forwarding the data packet from the routing path. Wireless sensor network system characterized in that. For each of the plurality of reference nodes having a wireless sensor, setting a primary path for data transmission and at least one alternative path for each reference node; Receiving, by any child node which is one of the plurality of reference nodes, a data packet transmitted from a blind node carried by a user and forwarding the data packet to a parent node corresponding to a default path; And In the event of a network failure, the child node changes the default path to an alternate path and forwards the data packet to another parent node again. Data communication method of a wireless sensor network system comprising a. The method of claim 7, wherein Receiving a data packet transmitted from a blind node carried by a user by any child node, which is one of the plurality of reference nodes, and forwarding the data packet to a parent node corresponding to a default path, Selecting, by the blind node, an initial transmitting node closest to the reference node; The blind node transmitting the data packet to the initial transmitting node; And Forwarding the data packet from the initial transmitting node along a default path of a plurality of reference nodes until a network failure is detected; Data communication method of a wireless sensor network system comprising a. The method of claim 8, In the blind node selecting an initial transmitting node of one of the reference nodes, The blind node selects a reference node having the highest Radio Signal Strength Information (RSSI) value as the initial transmission node. Data communication method of a wireless sensor network system, characterized in that. The method of claim 7, wherein each of the plurality of reference nodes, Actively varying wireless power depending on the distance between itself and the parent node that forwards the data packet Data communication method of a wireless sensor network system, characterized in that. The method of claim 10, wherein each of the plurality of reference nodes, Transmitting the data packet by increasing wireless power when the distance between itself and the parent node that forwards the data packet is more than two hops. Data communication method of a wireless sensor network system, characterized in that. The method of claim 7, wherein each of the plurality of reference nodes, Inspecting its own battery status and transmitting the data packet by lowering wireless power when the battery voltage is below the reference voltage Data communication method of a wireless sensor network system, characterized in that.