KR20100036918A - Method for wireless communication in sensor network environment - Google Patents

Abstract

PURPOSE: A method for wireless communication in a sensor network environment is provided to stably transmit sensor data by selecting a candidate node after transferring a transmission failure packet. CONSTITUTION: A neighbor sensor node of a source sensor node overhears the packet of the source sensor node(S110). In addition, the neighbor sensor overhears the response packet of the destination sync node(S130). The source sensor node overhears the packet of the transfer node(S160), and the transfer node transfers the transmission failure packet to the destination sync node(S150). The neighbor nodes of the transfer node judge the success of the packet transfer(S170).

Description

Method for wireless communication in wireless sensor network environment

The present invention relates to a wireless communication method in a wireless sensor network environment, and to an apparatus and method for transmitting a packet within a delay time in preparation for a packet transmission failure that may occur due to an obstacle in a wireless sensor network installed on a road.

The present invention is derived from a study conducted as part of the IT growth engine technology development project of the Ministry of Knowledge Economy [Task management number: 2006-S-024-03, Task name: USN infrastructure-based telematics application service technology development].

Nodes constituting the sensor network installed on the road must perform communication by adapting to the rapidly changing channel environment during inter-node communication. If there is an obstacle such as a vehicle between the transmitting node and the receiving node, the communication success rate between the two nodes drops to a significant level. As a result, it is impossible to predict the communication success rate between the transmitting and receiving nodes at the time of packet transmission of the transmitting node.

Conventional proactive routing (DSDV), Wireless Routing Protocol (WRP), Clusterhead Gateway Switch Routing (CGSR), and the like, proactive routing (Proactive routing) techniques periodically include a routing table containing the route information to the destination to the terminal Keep up-to-date route information by distributing. However, the proactive routing method has a problem in that the maintenance cost of the routing table is high and the route information must be periodically transmitted to the terminal regardless of the need for the route information.

Meanwhile, reactive routing techniques such as AODV (Ad hoc On-demand Distance Vector routing) and Dynamic Source Routing (DSR) find a route by flooding a RREQ packet whenever necessary. This technique requires high latency for initial path discovery time and excessive flooding is a problem.

As described above, both proactive routing and reactive routing have a common point of determining a route to a destination before packet transmission and then determining a next hop node on the route in advance. However, it is not suitable for a wireless sensor network system in a road environment where it is practically impossible to predict the communication success rate between the transmitting and receiving nodes at the time of packet transmission of the transmitting node.

Accordingly, the present invention provides a packet with high reliability in a predetermined delay time even if the communication success rate between the transmitting sensor node installed on the road and the receiving sink node installed on the roadside changes unpredictably, from the transmitting sensor node to the target sink node. An apparatus and method for transmitting are provided.

Communication method which is one feature of the present invention for achieving the technical problem of the present invention,

Determining, by a plurality of nodes, whether the destination sink node has received the packet; If the response packet has not been received, transmitting a packet eavesdropped by a forwarding node selected using local information among the plurality of neighbor sensor nodes to a target sink node.

Communication method which is another feature of the present invention for achieving the technical problem of the present invention,

Determining whether a response packet is received from the target sink node; If the response packet is not received, checking whether a forwarding candidate node selected from a plurality of neighbor sensor nodes that have eavesdropped the packet transmits the packet to the destination sink node; And eavesdropping the packet if the forwarding node sends the packet to the destination sink node instead of the source sensor node.

According to the present invention, even in an environment in which the physical communication success rate between the transmitting and receiving nodes varies variably due to the vehicle and other obstacles of the sensor node installed on the road, the generation of additional network overhead can at least stably transmit the sensor data.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

Throughout the specification, when a part is said to "include" a certain component, it means that it can further include other components, without excluding other components unless specifically stated otherwise. In addition, the terms “… unit”, “… unit”, “module”, etc. described in the specification mean a unit that processes at least one function or operation, which may be implemented by hardware or software or a combination of hardware and software. have.

Hereinafter, a wireless communication network and method according to an embodiment of the present invention will be described with reference to the drawings.

1 is a structural diagram of a wireless communication network according to an embodiment of the present invention.

As shown in FIG. 1, a communication network according to an embodiment of the present invention is configured in the form of a cluster tree. The root of the entire network serves as a base station, and the header of each cluster functions as a sink node. The sink node installed on the roadside has a plurality of sensor nodes and other sink nodes neighboring to the sink node as child nodes.

The sensor nodes installed in the center of the lane can successfully transmit packets to the roadside sink node when there is no obstacle between the sensor node and the sink node. However, if there is an obstacle such as a vehicle between the sensor node and the sink node, the packet transmission probability drops drastically.

In the communication network as described above, referring to FIG. 2 for a communication method capable of transmitting a packet within a predetermined delay time with high reliability even when a packet transmission success rate from the source sensor node to the destination sensor node is reduced by an obstacle or the like. It will be described as.

2 is a flowchart illustrating a wireless communication method according to an embodiment of the present invention.

As shown in FIG. 2, when the source sensor node attempts to transmit a packet to the target sink node (S100), the neighbor sensor node of the source sensor node taps a packet that the source sensor node attempts to transmit to the target sink node ( overhear) (S110). The target sink node receiving the packet from the source sensor node transmits a response packet (ACK) (S120). At the same time, the neighbor sensor node of the source sensor node also taps the response packet from the target sink node (S140).

The source sensor node determines whether a response packet is received from the target sink node (S150), and upon receiving the response packet, determines that the packet transmitted in step S100 is successfully transmitted. The neighboring sensor nodes that have eavesdropped both the packet sent by the source sensor node and the response packet sent by the destination sink node determine that the source sensor node has successfully sent the packet to the destination sensor node.

On the other hand, when the source sensor node transmits the packet but the destination sink node fails to receive the packet and does not transmit the response packet, the source sensor node determines that the packet transmission has failed. In addition, neighboring sensor nodes that have eavesdropped packets from the source sensor node but have not eavesdropped the response packets sent by the destination sink node to the source sensor node determine that the packet transmission from the source sensor node has failed.

If it is determined that the packet transmission from the source sensor node has failed, a neighbor sensor node selected from any one of the neighbor sensor nodes that has eavesdropped on the failed packet is transmitted to the destination sink node. Do it. In this case, a neighboring sensor node that transmits a packet that failed to transmit to the target sink node in place of the source sensor node is referred to as a forwarding node, and neighboring sensor nodes that have intercepted a transmission failure packet are referred to as a forwarding candidate node.

The source sensor node eavesdrops on the forwarding node transmitting the packet to the destination sink node (S160). When the source sensor node successfully intercepts the transmission of the packet of the forwarding node, the source sensor node determines that the packet has been transmitted to the destination sink node. On the other hand, when there is a transport packet other than the forwarded packet, the forwarding node may combine the two packets and transmit them.

The delivery candidate node is limited to some of the neighbor sensor nodes of the source sensor node, thereby minimizing energy consumption of the neighbor sensor nodes. The sensor node selected as the forwarding candidate node activates the receiver while the source sensor node transmits the packet to the destination sink node, and the packet sent by the source sensor node to the destination sink node and the response packet sent by the destination sink node to the source sensor node. You must eavesdrop.

Here, the forwarding candidate node is a neighbor sensor node that is closer to the destination sink node than the source sensor node among the neighbor sensor nodes of the source sensor node, and when the time division medium access control method is used, the time slot assigned to the source sensor node is assigned to the source sensor node. Neighbor sensor nodes that are prioritized over time slots.

When wireless communication is performed in a time division multiple access (TDMA) scheme, in the absence of an obstacle, a packet can be transmitted from a source sensor node to a target sink node with high reliability within a predetermined delay time. To this end, a communication system for communication in a time division medium access control method selects a node having time division of a medium and possesses a packet transmission authority in each time division time slot, and transmits schedule information including time slot transmission authority information to the entire network. Broadcast. At this time, each divided time domain is referred to as a time slot.

Schedule information of each time slot is generally included in beacon information and broadcasted to the entire network. Nodes receiving the beacon may know network schedule information. In the structure diagram shown in FIG. 1, sink nodes, which are cluster headers, broadcast schedule information about their child nodes in a beacon, and sensor nodes belonging to the same cluster receive schedule information of neighboring sensor nodes in the beacon. This can be seen through. That is, when communicating in a time-division media access control scheme, it is possible to know schedule information of itself and neighbor sensor nodes by receiving a beacon.

On the other hand, when the transmission candidate nodes communicate in a time division medium access control scheme, the guard for correcting the time synchronization error of the time slot assigned to the source sensor node without activating the receiver during the entire time slot period assigned to the source sensor node. Only active for the time and time for preamble reception. This minimizes energy consumption.

Meanwhile, some of the selected transfer candidate nodes are selected as final transfer candidate nodes based on the distance between the source sensor node and the target sink node and the allocated time slot information. This is based on at least one of transmission / receiving buffer length information or vehicle occupancy information of nodes selected from delivery candidate nodes immediately before the source sensor node transmits the packet, and selects some of the delivery candidate nodes as final delivery candidate nodes. This is to finally select candidate nodes.

That is, transfer candidate nodes are selected based on the distance between the source sensor node and the target sink node and the allocated time slot information. Then, if the vehicle occupies some forward candidate nodes among the firstly selected forward candidate nodes immediately before the forward sensor node transmits the packet, and even if the receiver is activated, the probability of packet eavesdropping from the source sensor node is reduced. The transfer candidate node occupied by the vehicle is finally excluded from the transfer candidate node.

Through this, power consumption required to eavesdrop the packet at the time of packet transmission of the source sensor node can be minimized by deactivating the transceiver. In addition, when the length of data in the transmission / reception buffer of some of the forwarding candidate nodes selected among the forwarding candidate nodes is larger than a predetermined threshold, the forwarding candidate node is excluded from the final forwarding candidate node.

If the packet transmission of the source sensor node fails, the forwarding candidate nodes should select one forwarding candidate node as the forwarding node. The forwarding node election is performed individually using only local information of each forwarding candidate node.

Each forwarding candidate node controls its position from the source sensor node and the destination sink node, which is the transmitting node at the time it is expected to transmit, whether the vehicle wheel is occupied, its communication buffer queue length, remaining battery amount and time-sharing media access control. In the case of the communication method, it is determined whether the eavesdropping packet is forwarded instead based on information such as the allocation time slot position.

When communicating with time-division media access control, the forwarding node has a time slot assigned to it, which is lower than the time slot assigned to the source sensor node, and is the fastest forwarding candidate node among the forwarding candidate nodes. And a forwarding candidate node closer to the destination sink node than the source sensor node, and a forwarding candidate node in which the vehicle wheel is not located directly above itself at the time of packet transmission. Then, by checking its communication buffer queue length at the time of packet transmission, a forwarding candidate node capable of transmitting an eavesdropping packet and having a sufficient amount of its remaining battery is selected as a forwarding node.

The selected forwarding node forwards the transmission failure packet to the target sink node instead (S150). The neighbor sensor nodes of the selected forwarding node tap the packet of the forwarding node to determine whether the packet transmission is successful (S170). The neighbor sensor node of the selected forwarding node also includes the origin sensor node that failed to transmit the packet.

When the selected forwarding node successfully forwards the failed transmission packet to the destination sink node and receives a response packet from the destination sink node, neighboring sensor nodes of the forwarding node including the source sensor node instead forward the forwarding packet and the response packet. Eavesdropping. Instead, the source sensor node tapping the forwarding packet and the response packet thinks that the selected forwarding node has successfully transmitted the packet to the destination sink node on its behalf, and discards the packet determined to be the forwarding failure (S180). The other forwarding candidate nodes of the source sensor node also think that the forwarding node that sent the packet on behalf of the source sensor node successfully transmitted the packet to the destination sink node, and discards the packet from the source sensor.

If one of the forwarding candidate nodes forwards the packet at the time of packet transmission, the wheel of the vehicle occupies the sensor, or the communication buffer queue length is too large to transmit the failed transmission packet of the source sensor node to the destination sink node instead. The candidate nodes eavesdrop on the packet transmission of the first priority forwarding node to recognize that the first priority forwarding node does not transmit the transmission failure packet of the source sensor node instead. The second priority forwarding node then forwards the transmission failure packet of the originating sensor node instead.

In the embodiment of the present invention, when using the time division media access control scheme, the first priority forwarding node is a forwarding candidate node assigned a time slot of a lower priority than the time slot assigned to the source sensor node. The second priority forwarding node is a forwarding candidate node allocated with a lower priority time slot than the first forwarding node.

If no delivery candidate node transmits a transmission failure packet to the destination sink node on behalf of the source sensor node, the source sensor node may retransmit the transmission failure packet at the next beacon interval. When the forwarding candidate node is selected in this manner, network overhead for selecting the forwarding candidate node does not occur, and the forwarding node is selected at the time of packet transmission instead of the method of determining the forwarding node at the time of packet reception. The packet transmission success rate can be increased even in an unpredictable channel situation.

Meanwhile, when receiving a packet, the destination sink node transmits a group response packet, which is a bitmap response packet for sensor nodes in the same cluster, to the sensor nodes. This has the effect of repeatedly transmitting a response packet within the same beacon interval. Through this, the reception probability of the response packet increases, and it is possible to effectively prevent duplicate transmission of the same packet.

In the embodiment of the present invention, the address of the child sensor node of the target sink node is aa11, aa22, aa33,... Assume that there are eight sensor nodes, aa88. Then, when receiving the packet generated by the child sensor node aa11, the target sink node sets and transmits a group response packet as shown in Table 1 below.

One 0 0 0 0 0 0 0

after. Upon receiving the packet generated by the child sensor node a33 within the same beacon interval, the group response packet is set and transmitted as shown in Table 2 below.

One 0 One 0 0 0 0 0

If the sensor node selected from the forwarding node successfully transmits the packet to the destination sink node instead, the forwarding candidate nodes that have not been selected as the forwarding node should discard the eavesdropping packet. That is, if one of the forwarding candidate nodes intercepts the forwarding failed packet to the destination sink node when the packet transmission failure of the source sensor node fails, the forwarding candidate nodes indicate that the forwarding candidate node that forwarded the packet is the forwarding node. To judge. The forwarding candidate nodes not selected as forwarding nodes discard the eavesdropping packet.

In this way, only one forwarding candidate node that forwards a transmission failure packet is selected among forwarding candidate nodes. Through this, other forwarding candidate nodes that are not selected as forwarding nodes discard the transmission failure packets by tapping packets of the forwarding node, thereby reducing network congestion and resource consumption due to redundant transmission of packets.

Meanwhile, the forwarding node becomes a source sensor node at the moment of transmitting a packet on behalf of the source sensor node, and an algorithm for increasing the packet transmission success rate by tapping from the source sensor node to the target sink node operates. On the other hand, the source sensor node receiving the response packet from the target sink node broadcasts a duplicate prevention packet immediately after the response packet in order to prevent duplicate transmission of the packet when neighboring forwarding candidate nodes do not receive the response packet.

The embodiments of the present invention described above are not only implemented by the apparatus and method but may be implemented through a program for realizing the function corresponding to the configuration of the embodiment of the present invention or a recording medium on which the program is recorded, The embodiments can be easily implemented by those skilled in the art from the description of the embodiments described above.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

1 is a structural diagram of a wireless communication network according to an embodiment of the present invention.

2 is a flowchart illustrating a wireless communication method according to an embodiment of the present invention.

Claims (9)

Eavesdropping packets sent from the source sensor node to the destination sink node; Determining, by a plurality of nodes, whether the destination sink node has received the packet; If the response packet is not received, transmitting a packet tapped by a forwarding node selected using local information among the plurality of neighbor sensor nodes to a target sink node. Wireless communication method comprising a. The method of claim 1, The forwarding node, Selecting a forwarding candidate node among the plurality of neighbor sensor nodes; And Selecting the forwarding node among the selected forwarding candidate nodes Wireless communication method comprising a. The method of claim 2, Selecting the forwarding candidate node, The distance between the source sensor node and the destination sink node of the plurality of neighboring sensor nodes is determined to be located closer to the destination sink node, and a time slot having a lower priority is assigned than the time slot assigned to the source sensor node. Selecting a node as the forwarding candidate node Wireless communication method comprising a. The method of claim 3, Selecting the forwarding candidate node, Just before the source sensor node wants to send a packet, Finally selecting some of the forwarding candidate nodes as final forwarding candidate nodes based on at least one of transmission / reception buffer length information and vehicle occupancy information of nodes selected as forwarding candidate nodes; Wireless communication method further comprising. The method of claim 2, Selecting the forwarding node, When it is determined that the forwarding candidate nodes transmit a packet, Prioritizing the plurality of delivery candidate nodes based on any one of distance information, time slot information, buffer length information, or occupancy information of the target sink node; And selecting a forwarding node from the higher priority nodes among the forwarding candidate nodes based on the priority. The method of claim 2, A forwarding candidate node eavesdropping a packet from the source sensor node, A method of wireless communication in which a receiver is activated only during a guard time for correcting a time synchronization error of a time slot assigned to a source sensor node and a time for receiving a preamble. Sending a packet to a destination sink node; Determining whether a response packet is received from the target sink node; If the response packet is not received, checking whether a forwarding candidate node selected from a plurality of neighbor sensor nodes that have eavesdropped the packet transmits the packet to the destination sink node; And Eavesdropping the packet if the forwarding node sends the packet to the destination sink node instead of the source sensor node Wireless communication method comprising a. The method of claim 7, wherein The response packet is a group response packet transmitted to a plurality of sensor nodes in the same cluster. The method of claim 7, wherein The forwarding node is selected from a forwarding candidate node whose time slot is lower than a time slot assigned to a source sensor node among the plurality of neighboring sensor nodes, or from a forwarding candidate node located closer to the destination sink node than the source sensor node. Wireless communication method.

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