KR101441476B1 - Method for Packet Routing in sensor network - Google Patents

Abstract

The present invention relates to a packet routing method in a sensor network, which takes into consideration location information of a neighboring node, information on energy level of a neighboring node according to time, and wireless channel state information between a current node and a neighboring node in a multi- And to provide a packet routing method capable of performing load balancing considering energy consumption of a node over time.

To this end, the present invention provides a packet routing method in a node of a sensor network, the packet routing method comprising: a table configuration step of configuring a neighbor table including position information of a peripheral node of the node, residual energy information, and wireless channel status information; A candidate group determination step of determining a candidate group of a node to receive a data packet transmitted from the neighboring nodes; And a node determining step of determining a node to receive a data packet transmitted by the node in the candidate group according to a location of the neighboring node, a remaining energy amount according to a flow of time, and a radio channel state based on information of the neighboring table Wherein the candidate group includes a node capable of receiving a packet without error from the node.

Wireless sensor networks, packet forwarding, routing

Description

[0001] The present invention relates to a packet routing method in a sensor network,

The present invention relates to a packet routing method in a sensor network, and more particularly, to a method of routing packets in a sensor network, and more particularly, to a method of routing packets in a sensor network, To a packet routing method for routing a data packet to an optimal path by using a cost function in which information is considered.

The wireless sensor network transmits sensing information from each sensor node to a predetermined destination, that is, a sink node (sink node or destination node). Here, the most important point is efficient use of energy, accurate information transmission, and high transmission efficiency.

In a wireless sensor network, when a current node transmits a packet to a next node, if a local optimal selection method for selecting an optimal node among neighboring nodes is repeatedly used for each node, an optimal path is selected to a destination and a packet is transmitted . Therefore, the most important thing in the location-based routing method is the decision of the next node.

Here, the next node is a node that receives a signal or a packet from the current node. Generally, from the viewpoint of a node, a packet includes a control packet that the current node processes as a source node or a destination node, There is a data packet for forwarding.

Conventionally, Greedy Perimeter Stateless Routing (GPSR) is a technique for determining a next node using location information of a neighboring node. A neighboring node closest to a destination node is selected as a next node, and a packet is transmitted to the next selected node. Also, when a packet is transmitted to a local minimum node, the next node is determined using a right hand rule to find another route to the destination. Here, the local minimum node means a node that does not have the next node to receive the packet.

Although the GPSR can perform routing using only the location information of the neighboring node without state information of the neighboring node, load balancing can not be performed at all, and nodes around the communication hole are continuously used There is a disadvantage that the number of communication holes increases.

Here, load balancing means that a packet is distributedly transferred to several nodes. In other words, it is possible to prevent concentration of energy of the specific node by preventing concentration of packet transmission to a specific node.

At the beginning of the sensor network, each node has sufficient energy, but over time, the energy consumed by each node is different. Since the residual energy for each node is different, load balancing is more important when time is more than the initial point of the sensor network.

Therefore, there is a need for a routing method that can consider the energy consumption of the node over time.

Meanwhile, the conventional GEAR (Greedy and Energy Aware Routing) is a technology for determining the next node by using the neighboring node location information and the energy remaining amount information of the neighboring node, and selects the node having the largest energy amount among the neighboring nodes as the next node .

Although the GEAR can perform load balancing using an energy aware method that configures a path in consideration of the remaining lifetime of a node and power consumed in data transmission, there is a disadvantage that energy consumption of each node is insufficient over time . In addition, there is a disadvantage in that a transmission error of a packet may frequently occur because no consideration is given to the state of a wireless channel.

In other words, routing techniques for performing load balancing using conventional energy balance information use a method of selecting the node farthest from the current node in the destination direction within the transmission range of the current node.

However, when a signal is transmitted to the node that is farthest within the transmission range of the current node, a problem occurs in relation to the actual wireless channel. In other words, as the transmission distance increases, the strength of the signal received by the receiving node decreases exponentially, so that the signal received by the receiving node may contain an error and can not be reliably transmitted to the receiving node May be included in the scope.

Accordingly, there is a need for a routing method capable of reducing the signal transmission error and the retransmission rate and providing the required quality of service (QoS) by selecting nodes within an error free range. In addition, a routing method considering the state of a wireless channel between nodes is required as well as neighboring node location information and energy remaining amount information of neighboring nodes.

As described above, the packet routing method for the multi-hop sensor network considers the location information of the neighboring node, the energy remaining amount information of the neighboring node, and the radio channel information between the current node and the neighboring node, Load balancing can be performed.

Accordingly, the present invention has been proposed in order to meet the above-mentioned demand. In the multi-hop wireless sensor network, consideration is given to location information of a neighboring node, energy remaining amount information of a neighboring node according to time, and wireless channel state information between a current node and a neighboring node And to provide a packet routing method capable of performing load balancing considering energy consumption of a node over time.

The objects of the present invention are not limited to the above-mentioned objects, and other objects and advantages of the present invention which are not mentioned can be understood by the following description, and will be more clearly understood by the embodiments of the present invention. It will also be readily apparent that the objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.

According to another aspect of the present invention, there is provided a packet routing method in a node of a sensor network, the packet routing method comprising: a table configuration step of configuring a neighbor table including position information, residual energy information, ; A candidate group determination step of determining a candidate group of a node to receive a data packet transmitted from the neighboring nodes; And a node determining step of determining a node to receive a data packet transmitted by the node in the candidate group according to a location of the neighboring node, a remaining energy amount according to a flow of time, and a radio channel state based on information of the neighboring table Wherein the candidate group includes a node capable of receiving a packet without error from the node.

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The present invention provides quality of service (QoS) required in a wireless sensor network and performs load balancing in consideration of energy consumption of a node over time, thereby determining an optimal path to a destination.

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings, Can be easily performed. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail. Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

There are several premises for applying the present invention. First, each node knows its location information by the GPS device and knows the sink node, that is, the destination information. Second, each node can keep track of the amount of residual energy by itself. Third, each node uses a simple hello protocol to periodically report information of neighboring nodes in one-hop.

Here, the simple hello protocol is a protocol for establishing and managing the relationship with neighboring nodes, and the one-hop is a link between one node and one node.

1 is a diagram showing an embodiment of a sensor network to which the present invention is applied.

As shown in FIG. 1, from the point of view of the current node 111, in theory, the current node 111 may send packets to a neighboring node as far as possible within its transmission range, but this is not the case in practice. The transmission range is classified into a connected region 101, a transient region 103, and a disconnected region 105 depending on the distance.

When a node to which a packet is to be transmitted (hereinafter referred to as a transmission node) transmits a packet to a neighboring node in the connection area 101, a packet can be transmitted without error. If a packet is transmitted to a neighboring node in the intermediate area 103, an error may occur. When a packet is transmitted to a neighboring node in the disconnection area 105, the packet can not be transmitted because of the environment of the wireless channel.

Therefore, the nodes outside the connection area 101 of the current node 111 are included in the indifferent node group (ING), and are excluded from candidates that can become the next node. Also, a node in the connection area 101 but having a low packet reception rate (PRR) is also included in the ING.

For example, the current node 111 includes the nodes of the intermediate area 103 and the disconnected area 105 as an ING (since it is a node outside the connection area 101) 101), a node having a small distance to the destination and a large energy amount is selected as the next node.

By selecting the next node among the nodes of the connection area 101, one-hop packet transmission error is prevented, and the re-transmission rate is reduced. As the retransmission rate is reduced, the energy consumption of the node is reduced, and the end-to-end delay from the transmitting node to the destination node is reduced, so that higher quality of service (QoS) can be provided.

In addition to the intermediate area 103 and the node inside the disconnecting area 105, a node 115 included in the connection area 101 but between the source node 111 and a node having a low PRR 113) is also included as ING, and is excluded from the next node candidate.

Here, the presence of the obstacle 115 between the nodes can be known by periodically exchanging a control packet. If a node with a low reception rate of control packets is found while the distance is close, it can be expected that an obstacle exists between the nodes or a radio channel situation is bad. Therefore, the discovered node reports to a node having a low PRR ING.

2 is a flow diagram of an embodiment of a routing method according to the present invention.

As shown in FIG. 2, the nodes are first placed, and each node sets the values of the nodes themselves. Here, the value of a node means position information, energy information, neighbor node information, etc. of each node.

The set initial information is recorded in a neighbor table (NT) and stored (s201).

First, the node IDs of all the nodes except the self, the position information of the node, the remaining energy, and the number of times the control packet is received are recorded. The position information of the node can be known by GPS, all the values other than the position information are set to 0, each node can know the residual energy by itself, and the initial energy of each node ) Are all the same.

The number of times the control packet is transmitted is recorded in order to check the PRR of the neighboring node by checking how many control packets are transmitted from the neighboring node during the transmission of the control packet. The received signal strength may be recorded instead of the number of times the control packet is received and used as PRR.

Currently, each node has not received information of neighboring nodes, so the ING table is not created.

In the ING table, a node ID having a low PRR, although in a node ID and a connected region outside the connected region, is described. The node included in the ING table is excluded from the next node candidate. Here, the reference of the connected region and the reference of the PRR are values set by the network administrator in the network configuration. For example, a radius of 10 m and a PRR of 80% can be set.

When the ING table is created, the NT table excluding the nodes included in the ING table from the initially created NT table becomes the next node candidate.

Next, it is determined whether a control packet is transmitted or received (s203).

As a result of the judgment of the step s203, when the control packet is transmitted / received (s213), it will be explained in detail in Fig.

If it is determined in step s203 that the control packet is not transmitted or received, it is determined whether the data packet is transmitted or received (step s205).

As a result of the judgment in the step s205, if a data packet is transmitted / received (s215), it will be explained in detail in Fig.

If it is determined in step s205 that the data packet is not transmitted or received, it is determined whether the current node has received the local minimum node (s207).

If it is determined in step s207 that the current node is the local minimum node, the current node is included in the ING (s217), and control returns to the control packet transmission / reception step (s203).

If it is determined in step s207 that the current node is not a local minimum node, it is checked whether the node energy of the current node is exhausted (s209). That is, it checks whether an energy depleted interrupt has occurred.

If it is determined in step s209 that the node energy of the current node is exhausted, it is determined that the network has reached the end of its lifetime and the algorithm is terminated (s211).

On the other hand, if it is determined in step s209 that the node energy of the current node is not exhausted, control returns to step s203.

FIG. 3 is a flowchart showing an example of a control packet transmission / reception (s213) of FIG.

The node periodically exchanges control packets. Each node periodically transmits a control packet to a neighbor node, receives a control packet from a neighbor node, and updates its own information, i.e., the NT table, set in step s201.

As shown in FIG. 3, first, it is determined whether a control packet is received (s301).

Next, if the control packet is received, it is determined whether the current node is a connected region of the node that transmitted the control packet and a node having a low PRR (S303).

If it is determined in step s303 that the current node is a connection area of the previous node and is not a node having a low PRR at the same time, the NT table is updated (s309). After updating the NT table, a standby state is reached (s311).

If it is determined in step s303 that the current node is a connection area of the previous node and has a low PRR at the same time, the current node is included in the ING (s305), and the standby state is reached (s311).

Next, if it is not the case that the current node has received the control packet, that is, if the control packet has to be transmitted, the current node transmits a control packet including the node information (s307) ).

When the current node generates a control packet, the generated control packet is transmitted to one hop (1 hop) neighboring node. A periodic timer is started for periodic control packet transmission.

4 is a flowchart illustrating an example of the case of the data packet transmission / reception (s215) of FIG.

Unlike a control packet transmitted to a node within one hop, the data packet is transmitted to any one of the neighboring nodes. In the case where a data packet is generated, a node itself generates data, and a data packet is transmitted from another node to the next node.

When a node generates data by itself, transmission of a packet from an upper layer is started, and transmission of a packet from a lower layer is started when a data packet is transmitted from another node.

The upper layer refers to a layer higher than a network layer having a routing mechanism, that is, an upper layer (for example, a transport layer, an application layer), and a lower layer Refers to a layer lower than the network layer having a routing mechanism, that is, a lower layer (for example, a MAC layer).

If there is a data packet to be transmitted, the current node selects the next node in the NT table. Here, a node outside the connected region, or a node with a low PRR, is included in the ING, and thus is excluded from the candidate that can be the next node.

Among the nodes included in the NT table, the next node is determined in consideration of the distance from the neighbor node to the destination node and the energy remaining amount of the neighbor node. Here, the relationship between the distance from the neighbor node to the destination node and the energy remaining amount of the neighbor node is defined as a cost function.

That is, among the nodes included in the NT table, the node having the lowest cost value by the cost function is selected as the next node.

The cost function is as follows.

The current node is called i-node, the neighboring nodes are called j-node, and the destination node is called d-node. Herein, the i-th node determines the next node as the node having the greatest energy remaining although it is closest to the d-th node among the j-th nodes.

First, a distance (D _ij ) between the j-th node and the d-node is obtained for all j-th nodes.

Where (x _d , y _d ) is the location of the destination node and (x _j , y _j ) is the location of the j node.

Next, the cost function appears by adding the normalized values of distance and energy. That is, the cost function _{(C j (d j, R} j)) is a function of the distance (d _j) and energy level (R _j).

는 모든 이웃 노드들의 에너지 합을 의미하고, R_j/

는 R_j의 정규화된 값을 의미한다.Here, z means the size of the network (the network is a circle with a radius z), and D _ij / z means the normalized value of D _ij . Also, _Rj denotes the energy remaining amount of the neighboring node j, and therefore,

Denotes the energy sum of all neighbor nodes, R _j /

Means the normalized value of R _j .

Also, β _i is an energy weighting factor, and it is possible to reflect the current energy amount due to energy consumption of each node to the cost function.

Using the cost function, a node having the smallest cost value C _j is selected as the next node, and a data packet is transmitted to the selected node.

On the other hand, the energy weighting factor (beta i) used in the cost function is as follows.

는 상기 NT 테이블에 포함된 모든 이웃 노드들의 현재 에너지 잔량(residual energy)의 합을 의미한다. 또한

는 상기 NT 테이블에 포함된 모든 이웃 노드들의 초기 에너지의 합을 의미한다.here,

Is the sum of the current energy residuals of all the neighbor nodes included in the NT table. Also

Is the sum of the initial energies of all neighbor nodes included in the NT table.

는 거의 1에 가깝고, 상기 β_i값은 0에 가까운 작은 값을 가지기 때문에 β 텀(term)은 미미한 정도여서, 초기 무선 네트워크의 노드는 거의 GPSR 방식의 라우팅을 한다.Initially, because the energy of all the nodes is full

Is near to 1, and since the value of β _i has a small value close to 0, the β term is insignificant, so that the nodes of the initial wireless network perform almost the GPSR routing.

는 거의 0에 가깝고, 상기 β_i값은 1에 가까운 큰 값을 가지기 때문에 β 텀이 고려되서, 무선 네트워크의 노드는 점점 더 크게 잔여 에너지량(R_j)의 영향을 받는 라우팅을 한다.However, as time passes, since the residual energy of the node becomes smaller gradually,

Is near 0, the _i value β is the β term doeseo considered because it has a large value close to 1, the nodes of a wireless network is increasingly routed largely affected by the residual amount of energy (R _j).

Generally, the packet is transmitted by selecting the next node by the cost function, but the packet is also transmitted. Or a local minimum, i.e., a communication hole.

The local minimum refers to a case where when a node selects a next node to transmit a packet, there is no node in the NT table excluding the ING node, and there is no next node to receive the packet, There is no node located in the node direction.

The destination node, i.e., the sink node, is generally predetermined. Therefore, in the process of creating the NT table, each node can know in advance whether there is a neighboring node located in the direction of the sink node, and if there is no neighboring node in the direction of the sinking node, Node. The local minimum node informs the neighbor node using the control packet that the neighbor node includes itself as ING.

If a packet is transmitted to the local minimum node, the local minimum node transmits the packet to the node having the largest remaining energy among the neighboring nodes. The neighbor nodes of the local minimum node include the local minimum node as ING and exclude the local minimum node from the next node candidate.

As shown in FIG. 4, first, a neighbor node included in the ING is excluded from the next node candidate (s401).

Next, it is determined whether there is a next node candidate, i.e., a node included in the NT table (s403).

If it is determined in step s403 that the next node candidate does not exist, the current node transmits information indicating that the current node is the local minimum node to the neighbor node (s413), selects the next node, And returns to the standby state (S415).

On the other hand, if it is determined in step s403 that the next node candidate exists, the distance (normalized value) between the neighbor node and the destination node is calculated (s405). Next, the ratio of the energy remaining amount (normalized value) of the neighbor node to the energy sum of all neighbor nodes is calculated (s407).

Next, the calculation results of the steps s405 and s407 are substituted into the cost function to calculate the cost, and the node having the smallest cost value is selected as the next node (s409).

Next, the current node transmits the data packet to the selected next node (s411), selects the next node, and ends the process of transmitting the data packet (S415).

FIG. 5 is a block diagram of a packet format used in FIGS. 1 to 4. FIG.

As shown in Fig. 5, the "SrcAddress" area is a part where the node that first created the packet records its node ID and records the location information (SrcPosX, SrcPosY).

The "DstAddress" area is a part for recording the ID and position information (DstPosX, DstPosY) of the destination node.

The "NxtAddress" area is a part for recording the ID and position information (NxtPosX, NxtPosY) of the next node.

The "RlyAddress" field selects the next node using the current node, that is, the EWG algorithm, and records the ID and position information (RlyPosX, RlyPosY) of the node transmitting the packet.

The "Residual Energy" field is a portion for recording the energy remaining amount of the current node. Therefore, the node receiving the packet can update the energy remaining amount information of the current node included in the own NT table.

The "Type" field is set to a different value to distinguish control packets and data packets.

On the other hand, of neighboring nodes that have received the control packet, neighbor nodes outside the connection region add the node ID to the ING table and include the node ID as ING. Since the location information of the transmitted node can be known using the information contained in the transmitted control packet, it is possible to confirm whether the neighboring node is a node outside the connection area.

Also, referring to the NT table, it is possible to know the number of times the control packet is transmitted in the connection area by referring to a predetermined hello protocol period. If the number of transmissions is less than or equal to a predetermined PRR% (for example, 80%), the corresponding node is also included as ING.

Meanwhile, the method of the present invention as described above can be written in a computer program. And the code and code segments constituting the program can be easily deduced by a computer programmer in the field. In addition, the created program is stored in a computer-readable recording medium (information storage medium), and is read and executed by a computer to implement the method of the present invention. And the recording medium includes all types of recording media readable by a computer.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. The present invention is not limited to the drawings.

1 is an embodiment showing a sensor network to which the present invention is applied.

FIG. 2 is a flowchart showing an embodiment of a routing method according to the present invention.

FIG. 3 is a flow chart of an embodiment showing a case of transmitting and receiving a control packet of FIG.

FIG. 4 is a flowchart showing an embodiment of the case of data packet transmission / reception in FIG. 2,

FIG. 5 is a block diagram of a packet format used in FIGS. 1 to 4. FIG.

Claims (15)

A method for routing a packet at a node in a sensor network, A table constructing step of constructing a neighbor table including position information of a peripheral node of the node, residual energy information, and wireless channel state information; A candidate group determination step of determining a candidate group of a node to receive a data packet transmitted from the neighboring nodes; And Determining a node to receive a data packet transmitted by the node in the candidate group according to a location of the neighboring node, a remaining energy amount according to a flow of time, and a radio channel state based on information of the neighbor table However, The candidate group includes: And a node capable of receiving a packet without error from the node. The method according to claim 1, Wherein the node determination step comprises: Wherein a node to receive a data packet transmitted by the node is determined by a cost function defined by the following equation (1). [Equation 1]

Where d _ij is the distance between j and d, D _ij / z is the normalized value of D _ij , β _i is an energy weighting factor, R _j is the energy remaining energy of neighboring node j, R _j /

Is the normalized value of R _j ,

Denotes the energy sum of all neighbor nodes) 3. The method of claim 2, D _ij , (2). ≪ / RTI > &Quot; (2) "

(Where x _d and y _d represent the position of the destination node, and x _j and y _j represent the position of the j node) The method of claim 3, The < _{RTI ID} = (3). ≪ / RTI > &Quot; (3) "

(here,

Is the sum of the current energy residuals of all the neighbor nodes included in the neighbor table,

Is the sum of the initial energies of all the neighbor nodes included in the neighbor table) delete The method according to claim 1, Wherein the node capable of receiving the packet without error, And a node included in a predetermined radius area centered on the node. The method according to claim 1, Wherein the node capable of receiving the packet without error, Wherein the packet reception ratio is a node having a predetermined reference value or more. 8. The method of claim 7, Wherein the node exchanges control information with the neighboring node to update the neighbor table Lt; / RTI > 9. The method of claim 8, Wherein the radio channel state includes: Wherein the number of times the node exchanges control information with the neighboring node. 10. The method of claim 9, The packet reception ratio And the number of times of switching is calculated based on the number of exchanges. 5. The method according to any one of claims 1 to 4, Receiving local minimum information from the peripheral node; And Excluding the neighboring node from the candidate group based on the received local minimum information Lt; / RTI > delete 5. The method according to any one of claims 1 to 4, Wherein the candidate group determination step comprises: And if there is no node included in the candidate group, transmits local minimum information to the neighboring node. delete delete

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