KR100954380B1 - Position based routing method using cell in wireless sensor network - Google Patents

Abstract

The present invention relates to a location-based routing method using a cell in a sensor network. In the wireless sensor network, an optimal next hop node is determined through contention by dividing a communication radius of a source node into cells and using a backoff time between nodes in each cell. By determining, it is possible to provide a location-based routing method using a cell in a wireless sensor network that can reduce the periodic communication for checking the location information to easily determine the route to the destination node while minimizing energy.

To this end, the present invention provides a location-based routing method comprising: a next hop position calculation step of calculating a virtual optimal next hop position (ONI) in a path to a destination node; A communication area zoning step of zoning its communication area into a predetermined cell size by using the calculated optimal next hop position; A packet broadcasting step of broadcasting a packet including the virtual optimal next hop position and the cell size to neighboring nodes in its communication area; And a next hop node determining step of receiving a response message for the broadcast packet from the neighboring node and determining a neighboring node that is initially transmitted as a next hop node.

Wireless sensor network, source node, destination node, cell, backoff time, inter-node contention, optimal next hop location information, optimal next hop node, location-based routing

Description

Location-based routing method using cell in wireless sensor network {POSITION BASED ROUTING METHOD USING CELL IN WIRELESS SENSOR NETWORK}

The present invention relates to a location-based routing method using a cell in a wireless sensor network. More particularly, the present invention relates to a cell-based routing method. By determining the next hop node of the present invention, it is possible to easily determine the route to the destination node while minimizing energy by reducing periodic communication for location information, and relates to a location-based routing method using a cell in a wireless sensor network.

The present invention is derived from a study conducted as part of the IT new growth engine core technology development project of the Ministry of Information and Communication and the Ministry of Information and Communication Research and Development. [Task Management Number: 2005-S-038-02, Title: UHF RF-ID and Ubiquitous Networking technology development].

Recently, in the sensor network, the number of nodes is larger than that of the ad-hoc network, and thus, communication collisions between nodes frequently occur during wireless communication. In the sensor network, the number of communication increases due to the retransmission of packets due to such collisions, and thus the transmission energy increases. Therefore, sensor networks require higher energy efficiency to reduce energy consumption than ad hoc networks. Moreover, since the nodes in the sensor network communicate using batteries, the efficiency of energy consumed by the nodes has become an important issue in the sensor network.

The proposed routing protocols in the sensor network can be divided into data-centric, hierarchical, and location-based routing protocols. In particular, in the location-based routing protocol, not only the sensor collects the information generated in the sensor network but also confirms the location information where the actual data is generated. Therefore, the location-based routing protocol occupies an important position in the routing protocol of the sensor network. On the other hand, as a technique for obtaining position information in the sensor network, a GPS (Global Positioning System), Received Signal Strength (RSS), or triangulation (Triangulation) is used.

Hereinafter, a conventional location based routing algorithm will be described.

1 is an explanatory diagram of a GPSR algorithm among the conventional location-based routing algorithm.

Conventional location-based routing algorithm is a GPSR (Greedy Perimeter Stateless Routing). The GPSR algorithm is an algorithm developed for location based routing in an ad hoc network.

The GPSR algorithm uses greedy forwarding. The GPSR uses the location information of the source node 10 and the location information of the destination node 12 for routing. The greedy forwarding refers to a method of delivering to the node 11 closest to the destination node 12 among the nodes within the communication radius 101 that the source node 10 can transmit. Accordingly, the GPSR algorithm periodically exchanges location information with neighboring hop nodes for greedy forwarding. This allows the source node to know the location information of neighboring nodes in its own hop. And every node periodically exchanges messages with nodes in one hop and manages the location information of neighboring nodes as a table.

When the source node 10 needs to transmit data, the source node 10 selects the node 11 closest to the destination node 12 by searching its own table managed as described above. The source node 10 transfers data to the nearest node 11. This process is applied repeatedly until data arrives at the destination node 12 to perform routing. In greedy forwarding, the source node 10 does not need to know the topology of the network as a whole, and only uses information of nodes in one hop of the source node 10.

Therefore, in the case of a multi-hop network, since the number of nodes in one hop is smaller than the number of all network nodes, the number of nodes that the source node 10 must manage is reduced compared to other routing methods.

If the number of nodes around the source node 10 is small and there are no nodes in the direction of the destination node 12, greedy forwarding may occur. In this case, a right-hand-rule is applied to transmit data (data for acquiring position information of a neighboring node). For example, source node 10 transmits data to Y node 11 located to its right, Y node 11 to Z node 13, and Z node 13 to D node 12. Send data to Thereafter, the D node 12 is transferred to the V (14) node, the V (14) node to the W (15) node, the W node 15 to the X node 10, and then the X node 10 is surrounded by Based on the information collected while returning to the W node 15 or Y node 11 to transmit the actual data to be transmitted.

However, this GPSR algorithm has a problem in that it wastes energy by increasing overhead due to periodic communication throughout the sensor network. That is, since the GPSR algorithm always exchanges location information with neighboring nodes even when there are no packets to be transmitted, the nodes continuously consume energy even if they do not participate in routing.

In addition, the source node must repeat the broadcast in order to exchange location information with neighboring nodes. This periodic broadcast method has a problem in that it affects the packet transmission by disturbing the communication between neighboring nodes.

The proposed algorithm to solve this problem of GPSR is OD-GPSR (On Demand GPSR) algorithm. The OD-GPSR algorithm does not always carry data in the sensor network, but only when an event occurs. And since the OD-GPSR algorithm sends data after event detection, the amount of actual data sent is less than that of the GPSR algorithm.

The OD-GPSR algorithm does nothing if there is no need to send data. Then, in the OD-GPSR algorithm, when data to be sent occurs, the node receives location information from neighboring nodes at that time. Therefore, the OD-GPSR algorithm can reduce energy consumption much compared to GPSR that sends and receives messages periodically.

However, the OD-GPSR algorithm has a problem in that the transmission delay time increases in the process of collecting the surrounding location information when data is generated.

2 is an explanatory diagram of a geo-back algorithm of a conventional location-based routing algorithm.

Geo-back (Geo-back: Geographical-Backoff) algorithm is an algorithm for solving the problem of periodically sending and receiving location information in the GPSR algorithm. The geo-back algorithm calculates a virtual node location called Optimal Nexthop Information (ONI) for routing using only its own location information without the location information of other nodes. To perform routing.

As shown in FIG. 2, the optimal next hop position information (ONI) 23 is the virtual position 23 closest to the destination node 22 in the transmission range 211 that the source node 21 can transmit. Say.

The optimal next hop location information 23 is a value that indicates where the source node 21 can send nearest to the destination node 22. The source node 21 having calculated this optimal next hop position information 23 broadcasts the optimal next hop position information 23 to nodes within one hop.

Nodes receiving the optimal next hop position information 23 calculate how far they are from the optimal next hop position information 23 and have different backoff times according to the value. Nodes located closer to the optimal next hop position information 23 have a shorter backoff time, so that a node closer to the optimal next hop position information 23 first responds to the optimal next hop position information 23. Send a message. The other nodes that were doing the contention think that the other node 24 has been selected when they hear the response message and stop the backoff. In this way, the source node 21 selects the node that sent the response message as the next node 24 and delivers the data to the selected node 24. This geo-back algorithm can reduce the routing messages that the GPSR algorithm sends and receive periodically, thereby increasing energy efficiency in the sensor network.

However, the geo-back algorithm uses a predetermined backoff time according to the distance from the optimal next hop position information 23 to determine the backoff time associated with the response message. This method of setting the backoff time has a problem in that the sensor network in which the topology changes frequently does not adapt to the topology change.

Therefore, the prior art as described above may have a problem in that energy consumption may be increased due to the periodic exchange of messages, and in particular, it may not be able to cope adaptively in a sensor network whose topology changes frequently. Is the task.

Therefore, the present invention reduces the periodic communication for checking location information by dividing the communication radius of the source node by cell unit in the wireless sensor network and determining the optimal next hop node through contention using the backoff time between nodes in each cell. It is an object of the present invention to provide a location-based routing method using a cell in a wireless sensor network that can easily determine a route to a destination node while minimizing energy.

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 above can be understood by the following description, and will be more clearly understood by the embodiments of the present invention. Also, it will be readily appreciated that the objects and advantages of the present invention may be realized by the means and combinations thereof indicated in the claims.

The present invention has been proposed to solve the above-mentioned problem. In the wireless sensor network, the communication node of the source node is divided into cells and the optimal next hop node is determined through contention using a backoff time between nodes in each cell. It is done.

More specifically, the present invention provides a location-based routing method comprising: a next hop position calculation step of calculating a virtual optimal next hop position (ONI) in a path to a destination node; A communication area zoning step of zoning its communication area into a predetermined cell size by using the calculated optimal next hop position; A packet broadcasting step of broadcasting a packet including the virtual optimal next hop position and the cell size to neighboring nodes in its communication area; And a next hop node determining step of receiving a response message for the broadcast packet from the neighboring node and determining a neighboring node that is initially transmitted as a next hop node.

In addition, in the present invention, if the response message is not received from the neighboring node in the next hop node determination step, the virtual optimal next hop position is moved to another point of the virtual circle corresponding to its own communication area, Another next hop node determination step of determining a next hop node is further included.

The present invention as described above, to minimize the overhead for routing in the sensor network, it is possible to minimize the energy consumption of the node by reducing the collision occurring during wireless communication and the number of communication, thereby extending the life of the network It can be effected.

In addition, the present invention has the effect of reducing the routing overhead by routing through a new location-based routing protocol using the cell and the backoff time, without having to periodically receive the position of the surrounding nodes.

In addition, the present invention has an effect of reducing the overall routing delay time by presenting a sleep / wake schedule in the MAC using a cross-layer technique.

BRIEF DESCRIPTION OF THE DRAWINGS 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, It can be easily carried out. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 is a flowchart illustrating a location-based routing method using a cell in a wireless sensor network according to the present invention.

A location-based routing method using a cell in a wireless sensor network according to the present invention will be described with reference to FIGS. 3 to 9.

First, briefly describing the present invention, the present invention uses a routing protocol in a sensor network in which sensor nodes know their location information. In addition, the present invention relates to a protocol for adaptively and dynamically routing and forwarding a packet to a sensor network having a high density and changing topology. In addition, the present invention applies a sleep schedule in a media access control (MAC) using a cross layer technique.

First, the present invention calculates the optimal next hop position information (ONI) and calculates the distance between the optimal next hop position information (ONI) and the next node to calculate the backoff time. The source node responds first to the next node. The difference from the geo-back algorithm described above is that the backoff time is determined in units of cells by setting a variable region called a cell rather than determining a backoff time using a predetermined table.

Briefly referring to FIG. 3, processes “302” to “309” indicate a process of transmitting a packet. Processes "311" to "320" represent a process of receiving a packet for optimal next hop position information (ONI), calculating a cell position, calculating a backoff time, and contending nodes.

Hereinafter, processes "302" to "309" which are operations of a node transmitting a packet will be described, and processes "311" to "320" will be described with reference to FIGS. 3 to 9.

First, a description will be given on the assumption that a node of the sensor network is in an idle state 301.

In the wireless sensor network, the location-based routing method using the cell is briefly described. In order to send a packet to a destination node, the source node calculates an optimal next hop location information (302) and calculates an optimal next node calculated as neighbor nodes. A message for hop location information is broadcasted (303). The source node then waits 304 to receive a response message to the message sent for a predetermined time from the neighbor nodes. Here, the neighbor node refers to the neighbor node within the communication radius of the source node.

Meanwhile, neighbor nodes receiving the optimal next hop position information in step 303 calculate a cell position value to which they belong (312) and calculate a backoff time based on the cell position value (313).

The neighbor nodes wait 314 for a time until the backoff time calculated in step 313 ends. Subsequently, neighboring nodes start contention between nodes in each cell using the backoff time (315). The contention between nodes waits until the neighboring nodes end the backoff time for their cell, and then transmits a response message to the source node.

At this time, if a response message for the optimal next hop position information transmitted from other nodes to the source node is received, the packet about the optimal next hop position information is deleted (317). In addition, other nodes except for the first node that transmits the response message to the source node in the inter-node contention in each cell delete the transmitted packet.

The node with the shortest backoff time is selected as an optimal next hop node and transmits a relay response message to the source node (316). During contention, the node with the shortest backoff time is likely to win the contention.

Meanwhile, the process of calculating the optimal next hop position information and the cell size will be described in detail. When a packet to be sent to the destination node occurs, the source node sets the source address and the destination address to the packet and provides the optimal next hop position information. It is calculated and set in the packet (302). That is, the source node calculates the optimal next hop position information and sets the address of the destination node, the address of the source node, and the cell size in the packet to be transmitted. At this time, in the present invention, the routing radius of the node is zoned using the size of the cell and the optimal next hop position information. The cell has a square shape and the length of one side is defined by the cell size value. At this time, in order to zone using the cell, the cell size must be determined first. The cell size is determined by the node density of one hop. In order to determine the cell size, the present invention undergoes the following process.

delete

When a network is first created, the sink node sends its location information throughout the network. Then, not only can every node know the location of the sink node, but it can also know the density of one hop of the node. Based on this density information, it is decided how many cells the communication radius should be divided into. In other words, based on the density of nodes in one hop, the cell is divided so that at least one node can fit in one cell.

In the present invention, a similar method to greedy forwarding is used for routing. The difference from the conventional greedy forwarding is that the next node to forward the packet is not selected using the location information of the neighboring nodes, but the next node is selected through contention of the neighboring nodes using the backoff time. Is that. To this end, in the present invention, the optimal next hop position information is calculated. The optimal next hop location information is a value representing the point closest to the destination node from which the source node can communicate.

4 is a diagram illustrating a method of calculating optimal next hop position information according to the present invention.

As shown in FIG. 4, the optimal next hop position information calculation process applied to the present invention takes the destination node 42 out of where the source node 41 can send in consideration of r, which is the communication radius of the source node 41. The position closest to is calculated by the optimal next hop position information (ONI) 43.

That is, the optimal next hop position information calculation process mathematically determines that the distance between the source node 41 and the destination node 42 is d. In addition, the optimal next hop position information calculation method determines the point 43 which divides between the source node 41 and the destination node 42 into r and d-r among the line segments having a predetermined distance d as the optimal next hop position information.

On the other hand, referring to the process "303" to "307" with reference to Figure 4, the source node 41 obtains the optimal next hop position information, and transmits the next next hop position information to the neighbor nodes through a message (303). That is, the source node 41 broadcasts a message about the optimal next hop position information to the neighbor nodes in the communication radius r.

Subsequently, the source node 41 transmits the best next hop position information to the neighbor node and waits until a response message for the best next hop position information is received from the neighbor node (304).

When the source node 41 receives the response message from the neighboring node, the source node 41 sets the address of the optimal next hop node included in the response message in the packet (305). In operation 305, the packet set in step 305 is transmitted to the address of the optimal next hop node.

The source node 41 resets the timer and performs the next scheduling according to the medium access control (MAC) schedule (307).

On the other hand, if there is no response from neighboring nodes, the source node 41 calculates Deadzone Avoidance-Optimal Nexthop Information (DA-ONI) in which the optimal next hop position information is rotated based on its position. In operation 308, the source node 41 broadcasts a message including the DA-ONI in a region corresponding to the first quadrant including the DA-ONI, similarly to the process "303".

As described above, the source node 41 calculates an optimal next hop position information (ONI) to transmit a packet and broadcasts the calculated optimal next hop position information to neighboring nodes. Nodes receiving the optimal next hop position information calculate the cell position to which they belong by using their position information and the optimal next hop position information. In this case, it is preferable that the node calculates the backoff time by dividing the cells in one quadrant based on the source node. If the cell is divided over the entire area, the node having the longest backoff time may have a backoff time of several seconds. In this case, it has a big impact on the latency, which can cause a decrease in the performance of the routing protocol.

Therefore, the node calculates the backoff time by dividing the cell into only one quadrant region. This is to reduce the delay in calculating the backoff time. If the routing fails because there are no nodes in the quadrant (hereinafter referred to as deadzone), a deadzone avoidance algorithm is used to overcome this.

Hereinafter, the dead zone avoidance algorithm described above in step 308 will be described with reference to FIG. 5.

5 is a diagram illustrating an embodiment of a dead zone avoidance algorithm for avoiding a dead zone according to the present invention.

The source node 51 performs routing by bypassing the area where there is no node by using Deadzone Avoidance-ONI (DA-ONI). That is, the source node 51 transmits a packet including the optimal next hop position information 511 and the optimal next hop position information 511 when a node in the quadrant region does not exist and does not receive a response message. Routing is performed by calculating the value of DA-ONI 512 which is rotated by an arbitrary angle (eg, 90 degrees, etc.).

That is, the dead zone avoidance algorithm is for performing routing by changing the optimal next hop position information 511 to another position within the transmission range. The source node 51 broadcasts the optimal next hop position information 511 and then returns DA-ONI 512, which is a value obtained by rotating the optimal next hop position information 511 when there is no response from neighboring nodes. Compute and broadcast the recalculated value. That is, when the source node 51 broadcasts the optimal next hop position information 511 and does not receive a response from other nodes even after all of the backoff time passes, the dead zone is formed in the optimal next hop position information 511. I think it is. When the source node 51 determines that there is a dead zone, the source node 51 routes the dead zone by avoiding the dead zone.

As shown in FIG. 5, when the DA-ONI algorithm is described as an embodiment applied to the present invention, the optimal next hop position information 511 is rotated by 90 degrees. Using this value, a routing path is formed around the DA-ONI. Therefore, the source node 51 can avoid the dead zone. In this case, even if there is no node around the optimal next hop position information 511, routing is possible by avoiding an area where there is no node. This DA-ONI algorithm is to increase the routing probability.

Meanwhile, after the source node broadcasts the DA-ONI, the source node waits for a response related to the DA-ONI value transmitted from neighboring nodes (309).

When receiving a response from the neighboring nodes, the process transitions to the above-described "305" process and repeats the process from "305" process.

Hereinafter, the process of receiving the packet including the optimal next hop position information 511, calculating the position of the cell, calculating the backoff time, and contending between nodes will be described in detail.

The neighbor node checks the type of the packet transmitted from the source node (311). The neighbor node calculates the cell value to which it belongs by using its location information and the optimal next hop location information 511 if it is related to the transmission request according to the check result 311 (312).

In operation 313, the neighboring node calculates a backoff time based on the cell value calculated in step 312.

Here, a process of dividing cells based on the optimal next hop position information will be described with reference to FIG. 6.

6 is a diagram illustrating an embodiment of dividing a cell based on optimal next hop position information according to the present invention.

The present invention selects the node closest to the optimal next hop position information 62 based on the optimal next hop position information 62 as the next node in order to find the optimized node as the next node on the routing path. According to the present invention, the backoff time is set differently according to the distance from the next next hop position information 62, and the nodes perform contention for communication with the source node using the set backoff time. In order to calculate the backoff time from the optimal next hop position information 62 value and the position of the node, the present invention calculates the backoff time in units of cells by dividing the communication radius of the source node 61 into several cells. The method to calculate the position of a cell to which a node belongs is as follows.

The node divides the distance between the x coordinate of the optimal next hop position information 62 and the x coordinate of the node by the size of the cell 611 and the y coordinate of the node and the y coordinate of the node. Calculate the quotient of distance divided by cell size. These values indicate the number of cells in the x and y axes from the optimal next hop position information 62. Therefore, through this value, a node can know which cell it belongs to. After calculating the position of the cell, the node calculates the backoff times (T to 8T) in order according to the position value of the cell. That is, nodes that have received the optimal next hop position information 62 calculate which cell they belong to by using the optimal next hop position information 62, the size of the cell 611, and their location information. Calculate the backoff time according to the location.

Nodes in different cells have different backoff times depending on the location of the cell. In this way, it is possible to efficiently route by changing the size of the cell in accordance with the sensor network is changing the topology of the network.

Calculating the backoff time by dividing the cell is done only for the nodes in the quadrant to which the optimal next hop location information belongs. This is because in a dense sensor network, nodes in one quadrant are sufficient for routing. If a failure occurs due to routing for only one quadrant, the present invention determines that there is a dead zone and uses an algorithm to avoid it. This dead zone algorithm is as described above in FIG.

On the other hand, when the backoff time elapses (314), the nodes start contention in response to the node which sent the packet including the optimal next hop position information (315). That is, it waits according to the calculated backoff time and sends a response message to notify the source node when the backoff time passes.

On the other hand, if the neighboring node first transmits a response message for the optimal next hop position information, the node stops contention, deletes the packet (317), and returns to an idle (Idle) state to not send a response. The source node receiving the response to the optimal next hop position information selects the next node and transmits the data to the selected next node.

The node receiving the data checks the destination address (318) to determine whether the address of the destination node is the address of the local node, that is, its own address (319). The node transmits the packet to the upper layer if the packet comes to it (320), and if the packet goes to another destination, the node transmits the optimal next-hop position information to the destination node and repeats the process "302" to find the next node. In other words, when receiving data from the source node, it checks the destination node and if it is the destination node, sends a packet to the upper layer. Execute repeatedly from.

Hereinafter, a sleep / wake scheduling method will be described with reference to FIG. 7.

7 is a diagram illustrating an embodiment of a sleep and wake scheduling method in a MAC terminal according to the present invention.

In the sleep and wake algorithm, the sleep cell wakes up after a certain time and communicates. The wake-up cell repeatedly sleeps after a certain time. This is to save node energy by minimizing collision in MAC and reducing packet reception in idle state.

The basic operation of the MAC follows the same method as the IEEE 802.11, but the sleep and wake scheduling in the MAC is performed using the cell created during routing. Most sensor network MAC protocols use periodic sleep schedules. At this time, if the density of the node is high in the sensor network, collisions occur during communication between nodes. Then, since the node retransmits the packet, the number of communication of the node increases, which increases the energy consumption of the node.

In order to solve this problem, the present invention reduces the collision occurring during communication by distinguishing the sleeping area and the waking area by cell units. Nodes in a sleep cell reduce the energy consumption of the node by turning off the transceiver without participating in routing.

In this sleep and wake algorithm, nodes receiving a packet containing the optimal next hop position information repeat sleep and wake up according to their cell position. In the present invention, the cell position calculated during routing using the cross-layer scheme is used for the MAC protocol.

As shown in FIG. 7, in the present invention, nodes in a specific cell area in a cell unit enter a sleep mode, and other cells perform routing while maintaining a wake state. This scheduling method increases the latency of the network. The present invention uses a new sleep scheduling method using a cross-layer technique to reduce the delay time.

That is, in the present invention, each node sleeps or becomes active according to the position of the cell using the cell calculated while routing. If all nodes sleep at the same time, network latency continues while they sleep.

However, in the present invention, since the sleep schedule is determined on a cell basis, since there is always an active node in the network, delay time due to the sleep schedule can be reduced. In addition, the present invention can reduce the number of nodes in the active state by controlling the number of nodes.

At this time, the duty cycle of the node varies depending on the sleep and active patterns. The case where the sleep and active patterns are changed each time is shown in FIG. In this case, the activity cycle is 50%. In another embodiment, if the nine cells are bundled together and a pattern is set such that only one node of the nine cells operates, the activity period is 11%.

Hereinafter, a comparison between the present invention and the conventional GPSR algorithm is as follows.

The present invention relates to an algorithm for adaptively coping with a network with a high density of nodes and a changing topology. By comparing the present invention with the conventional GPSR algorithm, the degree of optimization to the node density and topology change will be analyzed.

In the conventional GPSR algorithm, since the location information is periodically exchanged with neighbor nodes, the GPSR routing overhead is represented by Equation 1 below.

Here, E [n] represents the number of neighboring nodes corresponding to one hop, E [h] represents the number of hops to an average destination, and E [t] represents an update message period between neighboring nodes for GPSR.

The GPSR routing overhead is proportional to the packet size, the number of neighboring nodes corresponding to one hop, the number of hops to the average destination, and inversely proportional to the update message period between neighboring nodes for GPSR.

In order to determine the location of a next hop node corresponding to one hop, the CBT overhead according to the present invention uses two messages necessary for positioning, optimal next hop position information, and a response message. Therefore, the routing overhead for the present invention can be defined as shown in Equation 2 below.

Where E [h] is the number of hops to the average destination and E [d] is the traffic data rate.

Since the present invention uses the back off time, a delay time occurs. This delay is the product of the average value of which node in the cell is selected and the base unit value of the backoff time. Therefore, it can be represented by the following formula (3).

Here, E [slot] represents the expected number of backoff slots.

Based on Equation 3 above, in order to indicate in which environment GPSR and CBT are more useful, Efficiency Ratio is defined as shown in Equation 4 below.

Based on the above Equation 4, when the graph is drawn while changing the density of the node and the message exchange period with the neighboring nodes of the GPSR, a result as shown in FIG. 8 is obtained.

FIG. 8 is a result diagram of an embodiment of an efficiency ratio according to a density of nodes and a message exchange period with neighboring nodes of a GPSR.

As shown in FIG. 8, it can be seen that the higher the number of nodes per hop, the more efficient the CBT according to the present invention. In addition, the message exchange period of the GPSR is related to the mobility (Mobility) of the node. As the value is larger, the period of exchanging the message is longer, so the mobility is low. Therefore, it can be seen that CBT is more efficient when the node is dense and the node is mobile, while GPSR is more effective when the node is low and no mobility.

DA-ONI represents a value in which the optimal next hop position information is rotated by a certain angle in order to avoid this when there is a dead zone. At this point, two factors must be considered to analyze how best to rotate the angle.

First, when the optimal next hop position information is rotated by θ, how wide the next hop position information can be given to the wide area. It is necessary to maximize this value because the higher the next hop location information is reported for a large area, the higher the probability of successful routing. The second thing to consider is how much more distance you need to travel with DA-ONI than when routing with optimal next-hop location information. It is necessary to minimize the return distance because the larger the rotation angle θ from the optimum next hop position information, the farther it should turn. To do this, each value is calculated as follows.

Regardless of the d value, when θ is 90 degrees, the smallest value can be seen. Therefore, it can be seen that it is most efficient to rotate θ by 90 degrees.

The simulation was performed using 'OPNET 11.0'. Table 1 below shows the parameters related to the simulation.

9 is a comparison diagram of a simulation result to which a conventional GPSR algorithm and a location-based routing method according to the present invention are applied.

As shown in FIG. 9, it can be seen that the routing success probability is low in the GPSR as a whole. This is because GPSR generates many broadcasting messages in order to periodically exchange location information with neighboring nodes. Therefore, GPSR can be found to have poor performance when network density increases.

On the other hand, in the case of the protocol according to the present invention, the higher the transmission range of the node, that is, the higher the density of the network, the better the routing success rate. The protocol according to the present invention shows a high probability of routing success even if the node density is high because little overhead for routing occurs.

The figure on the right shows the packet latency. Since the protocol according to the present invention uses a backoff time for routing, it is natural that the delay is larger than that of the GPSR. As shown in the figures, the protocol according to the present invention has a large delay time. However, the denser the network, the closer the latency becomes to GPSR. This is because the backoff time is very short when the node is located in the first cell.

On the other hand, 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 inferred by a computer programmer in the art. In addition, the written program is stored in a computer-readable recording medium (information storage medium), and read and executed by a computer to implement the method of the present invention. The recording medium may include any type of computer readable recording medium.

The present invention described above is capable of various substitutions, modifications, and changes without departing from the technical spirit of the present invention for those skilled in the art to which the present invention pertains. It is not limited by the drawings.

1 is an explanatory diagram of a GPSR algorithm of a conventional location-based routing algorithm;

2 is an explanatory diagram of a geo-back algorithm of a conventional location-based routing algorithm;

3 is a flowchart illustrating a location-based routing method using a cell in a wireless sensor network according to the present invention;

4 is an exemplary explanatory diagram for a method of calculating optimal next hop position information according to the present invention;

5 is an exemplary explanatory diagram of a dead zone avoidance algorithm for avoiding a dead zone according to the present invention;

6 is a diagram illustrating a process of dividing cells based on optimal next hop position information according to the present invention;

7 is a diagram illustrating an embodiment of a sleep and wake scheduling method in a MAC terminal according to the present invention;

8 is a diagram illustrating an embodiment of an efficiency ratio according to a density of a node and a message exchange period between neighboring nodes of a GPSR;

9 is a comparison diagram of a simulation result to which a conventional GPSR algorithm and a location-based routing method according to the present invention are applied.

* Explanation of symbols on the main parts of the drawing

41: source node 42: destination node

43: optimal next hop position information 512: DA-ONI

Claims (6)

delete delete In the location-based routing method, An imaginary optimal next hop position (ONI) is calculated by calculating a position of an imaginary line segment connecting the distance from the target node to the destination node and a point where the imaginary circle corresponding to the communication area meets. A next hop position calculation step of calculating Nexthop Information; The communication zone is zoned to a predetermined cell size by using the calculated optimal optimal next hop position, and the zoning includes the virtual optimal next hop position among the own communication areas and has a predetermined center angle. A communication area zoning step of zoning the communication area to a cell size; A packet broadcasting step of broadcasting a packet including the virtual optimal next hop position and the cell size to neighboring nodes in its communication area; And A next hop node determining step of receiving a response message for the broadcast packet from the neighbor node and determining the first neighbor node as the next hop node. Location-based routing method using a cell in a wireless sensor network comprising a. The method of claim 3, wherein If the response message is not received from the neighboring node in the next hop node determination step, another virtual node determines another next hop node by moving the virtual optimal next hop position to another point of the virtual circle corresponding to its own communication area. Next hop node determination steps Location-based routing method using a cell in a wireless sensor network further comprising. The method of claim 4, wherein The peripheral node, And a response message for the broadcast packet according to the backoff time of the cell to which the cell belongs. The method of claim 5, The backoff time of the cell, The location-based routing method using a cell in a wireless sensor network, characterized in that calculated according to the distance from the cell to which the peripheral node belongs to the virtual optimal next hop position.

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