KR101104585B1 - Method for Cross-Layered Routing and Transmitting Data in Wireless Sensor Network - Google Patents

Abstract

A cross layer based routing and data transmission method in a wireless sensor network is disclosed. The disclosed method comprises the steps of (a) receiving a synchronization packet from neighboring nodes comprising a routing length corresponding to a hop count with a sink node and a routing cost corresponding to the energy efficiency of the node; Checking routing length information included in the received synchronization packets and selecting a node having the smallest routing length as an upper node; In step (b), if the number of nodes having the shortest routing length is plural, step (c) as an upper node for selecting a node having the smallest routing cost; (D) setting a routing length to be increased by 1 than the selected node, calculating and setting a routing cost of the node itself, and broadcasting a synchronization packet including the set routing length and routing cost to neighboring nodes; Include. According to the disclosed method, a routing tree may be formed in a node synchronization step, and there is an advantage of improving energy efficiency and reducing transmission delay in data transmission.

Routing, Sensor Networks, MAC

Description

Method for Cross-Layered Routing and Transmitting Data in Wireless Sensor Network}

The present invention relates to a cross-layer-based routing and data transmission method in a wireless sensor network, and more particularly, to a data transmission method capable of more efficiently forming a routing tree and increasing energy efficiency.

The most representative competition-based synchronous MAC protocols in wireless sensor networks are S-MAC and T-MAC. The contention-based synchronous MAC protocol is a mechanism to reduce the unnecessary energy consumption in conventional wireless network communication by performing synchronization between nodes using synchronization packets and repeating active and sleep states periodically. .

S-MAC is a contention-based MAC protocol based on RTS (Clear To Send) / CTS (Clear To Send), and a synchronization cluster is used to configure a virtual cluster between nodes using synchronization packets to manage schedules. One frame consists of an active period and a sleep period. During the sleep period, the sensor nodes temporarily turn off the transceiver. In this state, data is not transmitted and stored. During the active period, the transceiver is turned on again, sending stored data or receiving data from neighboring nodes.

In this way, the duty cycle is a method in which the active and sleep cycles are repeatedly performed at a predetermined ratio. S-MAC uses these duty cycle techniques and virtual cluster schedule synchronization to reduce communication overhead and improve energy savings. The T-MAC adds a timer function to the S-MAC method, so if an event does not occur for a specified time, it will time out and the sensor nodes will go to sleep immediately, further saving energy. However, the S-MAC method has a disadvantage in that the data transmission delay is relatively increased.

Meanwhile, the most representative routing protocols in wireless ad hoc sensor networks are AODV (Ad hoc On-demand Distance Vector Routing, RFC3561) and DSR (Dynamic Source Routing, RFC4728). AODV routing is a technique that is performed only when nodes need routing, and when a source node wants to send a data packet to a destination, the node checks a routing table to determine whether the path exists. If no route is set, the route setting procedure to find the route to the destination is performed on-demand. The advantage of this method is that the signaling overhead can be reduced compared to the proactive method.

In AODV, if there is no proper route in the routing table, the source node generates a route request packet (RREQ: Route REQuest) to set up the route. In the case of a node that knows a route to a destination, a route reply (RREP) message is generated and transmitted back to the source node through a reverse path. If the link is down, the node closest to the source node treats the downed route invalid and generates a Route ERRor (RERR) message. The RERR message is sent to the source node via the reverse path, setting up a new path if necessary.

 DSR is similar to AODV but uses source routing. In DSR, instead of hop-by-hop routing, data packets contain source paths that define the path to the destination. In addition, to reduce routing costs, each node maintains a cache of source paths. The disadvantage of this on-demand routing is that there is a delay at the beginning of the data transfer due to routing. In addition, the conventional routing protocol is performed after the synchronization of each node, there is a problem that takes a separate time for synchronization and routing.

In order to solve the problems of the prior art as described above, an object of the present invention is to propose a cross layer-based routing and data transmission method in a wireless sensor network in which a routing tree can be formed in a node synchronization step.

Another object of the present invention is to propose a cross-layer based routing and data transmission method in a wireless sensor network capable of improving energy efficiency and transmission delay.

Other objects of the present invention will be readily apparent to those skilled in the art through the following examples.

In order to achieve the above object, according to an aspect of the present invention, a synchronization packet including a routing length corresponding to a hop count with a sink node and a routing cost corresponding to the energy efficiency of the node is received from neighboring nodes. (A); Checking routing length information included in the received synchronization packets and selecting a node having the smallest routing length as an upper node; In step (b), if the number of nodes having the shortest routing length is plural, step (c) as an upper node for selecting a node having the smallest routing cost; (D) setting a routing length to be increased by 1 than the selected node, calculating and setting a routing cost of the node itself, and broadcasting a synchronization packet including the set routing length and routing cost to neighboring nodes; A cross layer based routing and data transmission method in a wireless sensor network is provided.

The other node receiving the sync packet broadcast in step (d) repeats steps (a) to (d) to form a routing tree structure in the sync step.

The routing cost r_cst may be calculated using the following equation by using the unit data transmission cost C _T and the energy cost C _E of the node corresponding to the initial energy and the remaining energy ratio of the node.

In the above equation, α and β are weights having a value between 0 and 1, including 0 and 1.

The above-described method may include setting a routing length to a maximum value and broadcasting a link error packet including the set routing length when a link with an upper node is lost; And when receiving a sync packet from a neighbor node, resetting a path by using the routing length included in the sync packet and information of the neighbor node.

In addition, the above-described method, if receiving a link error packet indicating a link loss from another node, determining whether or not the link loss state; If not in a link lost state, sending a sync packet including the routing length and a routing cost to the node that transmitted the link error packet; And broadcasting the link error packet to the neighbor node when the link is lost.

The above-described method may include transmitting a Preoccupied Ready To Send (PRTS) packet to an upper node when overhearing a CTS (Clear To Send) packet from a lower node;-The upper node is in a sleep state in the PRTS packet Includes basic information for determining a time to maintain the data; when overhearing an ACK packet from the lower node, transmitting and transmitting a CTS packet to the lower node to initiate data transmission and reception with the lower node; The upper node determines the deactivation time using the basic information and maintains the deactivation state for the determined time.

When the deactivation state of the upper node is terminated, the method may further include receiving a CTS packet from the upper node and performing data transmission / reception with the upper node.

According to another aspect of the present invention, in a node device configuring a network for cross-layer based routing and data transmission in a wireless sensor network, a routing length and a node transmitted from other nodes and corresponding to a hop count with a sink node A sync packet receiver configured to receive sync packets including a routing cost corresponding to the energy efficiency of the apparatus; A routing path setting unit which selects an upper node using the routing length and the routing cost; A routing length setting unit configured to increase a routing length by one as compared with the selected upper node; A routing cost setting unit configured to calculate a routing cost using a unit data transmission cost C _T and an energy cost C _E of the node corresponding to the initial energy and the remaining energy ratio of the node; Cross-layer-based routing in a wireless sensor network including a synchronization packet transmitter for broadcasting a synchronization packet including a routing length set in the routing length setting unit and a routing cost set in the routing cost setting unit to neighbor nodes; There is provided a node device constituting a network for data transmission.

According to another aspect of the present invention, in the method of transmitting data in a wireless sensor network, when overhearing a CTS (Clear To Send) packet from a lower node, transmitting a Preoccupied Ready To Send (PRTS) packet to a higher node ;-The PRTS packet includes basic information for determining the time when the upper node maintains a sleep state.- When overhearing an ACK packet from the lower node, the CTS packet is transmitted to the lower node. Including a step of initiating data transmission and reception with a lower node, the upper node is provided with a data transmission method in the wireless sensor network to determine the deactivation time using the basic information, and maintains the deactivation state for the determined time.

According to the present invention, a routing tree may be formed in the node synchronization step, and there is an advantage of improving energy efficiency and reducing transmission delay in data transmission.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the cross-layer-based routing and data transmission method in the wireless sensor network according to the present invention.

1 is a diagram illustrating a field configuration of a sync packet according to an embodiment of the present invention.

Referring to FIG. 1, a sync packet (eg, a beacon packet) according to an embodiment of the present invention may include a sync signal field 100, a device information field 102, a channel state information field 104, It may include a routing length field 106 and a routing cost field 108.

In FIG. 1, the sync signal, device information and channel state information are information included in a sync packet common in the sensor network. Here, the synchronization signal is a signal for synchronization between nodes and synchronization of nodes included in the network is performed in correspondence with the synchronization signal included in the synchronization packet.

The first sync packet is broadcast by the sync node of the network, and the synchronization of the nodes by the sync packet is performed in such a manner that the nodes receiving the sync packet from the sink node broadcast the sync packet to neighboring nodes again.

In the present invention, such a synchronization packet further includes a routing length and a routing cost. The routing length and routing cost additionally included in the synchronization packet are information added to form a routing tree during synchronization of nodes.

The routing length refers to the hop count with the sink node, and the routing cost refers to the energy cost for routing. According to an embodiment of the present invention, the routing cost may be composed of two parameters, the unit data transmission cost C _T and the energy cost C _E of the node. Here, the energy cost C _E may be defined as the ratio of the initial energy of the node to the energy remaining.

Equation 1 below shows an example for calculating a routing cost r_cst added to a sync packet in the present invention.

In Equation 1, α and β are weights having a value between 0 and 1 including 0 and 1, and serve as weights for setting an association value between unit data transmission cost and node energy cost. α and β can be appropriately set according to the communication area characteristic.

According to an embodiment of the present invention, the routing length and the routing cost may be allocated 1 byte, respectively, the routing length may have a value of 0 to 255, and the routing cost may also have a value of 0 to 255. Of course, it will be apparent to those skilled in the art that the number of bits allocated to the routing length and the routing cost and the range of the routing length and the routing cost can be changed as necessary.

In the present invention, the node receiving the synchronization packet sets its own upper node using the routing length and routing cost information included in the synchronization packet, and through this, the routing tree formation can be performed together with the synchronization of the nodes.

2 is a flowchart illustrating a process of forming a routing tree by determining a higher node of a specific node of a network.

Referring to Figure 2, a node in the network receives a synchronization packet that includes a routing length and a routing cost (step 200). In this case, the node may receive a synchronization packet from a plurality of other nodes, and checks routing length information of each synchronization packet.

When receiving a plurality of sync packets, the node selects a node having the smallest routing length among the nodes that have sent the sync packet (step 202).

If there is contention because the node having the smallest routing length is 2 or more (step 204), the node checks the routing cost information of the sync packet transmitted by the contention nodes, and the node having the least routing cost among the contention nodes. Selects as its parent node (step 206).

When the parent node is selected in the routing tree by steps 200 to 206, it sets its routing length and routing cost. The routing length may have a value increased by 1 than the selected upper node, and the routing cost may be calculated by Equation 1 above.

Once the routing length and routing cost have been established, the node broadcasts to the neighboring nodes a sync packet containing the set routing length and routing cost (step 210).

Neighbors that receive the sync packet from the corresponding node may set their own upper node by the same method as in steps 200 to 206, and if such a process is performed to the lowest node, a routing tree of the network may be formed.

3 is a diagram illustrating an example of a routing tree structure formed by routing setup using a sync packet according to an embodiment of the present invention.

In FIG. 3, (a) shows a sequence in which sync packets are broadcast, and (b) shows a routing tree structure formed using sync packets. The parenthesis shown next to each node represents the hop count (ie routing length) from the sink node.

In Figure 3, node i receives sync packets from node g and node h. Node i receives sync packets from nodes g and h to check the routing length and routing cost. Since node g and node h have the same routing length, node i selects an upper node by the routing cost, and FIG. 3 (b) shows a case where node h is selected as an upper node.

Such a routing configuration method of the present invention has an advantage of not having to perform an additional process for routing path setting because the routing path is set in the MAC layer using a sync packet.

In addition, since the routing tree is managed using only local information and neighbor node management tables, the entire tree structure is not maintained by a specific node. Therefore, there is an advantage that there is no overhead according to the entire tree structure management.

When the tree structure is formed, a node that needs to transmit data to the sink node is transmitted to a higher node of the configured routing tree, and this process is repeated, and eventually data is transmitted to the sink node through the routing tree.

4 is a block diagram showing a configuration of a network node to which a cross-layer based routing configuration according to the present invention is applied.

Referring to FIG. 4, a node to which the method of the present invention is applied includes a synchronization packet receiver 400, a routing path setting unit 402, a routing length setting unit 404, a routing cost setting unit 406, and a synchronization packet transmission unit ( 408).

The sync packet receiver 400 receives a sync packet transmitted from other nodes of the network. As mentioned above, one or more sync packets may be received.

The routing path setting unit 402 selects an upper node using routing length information and routing cost information included in the received synchronization packets. As described above, the upper node is first selected by the routing length information, and when the nodes having the smallest routing length are contended, the upper node is finally selected by using the routing cost information.

The routing length setting unit 404 sets the routing length of the node itself, and sets the routing length so that 1 has an increased routing length compared to the selected upper node.

The routing cost setting unit 404 sets the routing cost by using the node energy cost defined as the ratio of energy required for unit data transmission and initial energy and remaining energy.

The sync packet transmitter 408 broadcasts a sync packet including the routing length set by the routing length setting unit 404 and the routing cost information set by the routing cost setting unit 406.

 FIG. 5 is a flowchart illustrating a procedure for recovering a path when a link is lost due to a node's movement or loss of function according to an embodiment of the present invention. FIG. 6 is a diagram illustrating a process of restoring a path in a routing tree. It is also.

 In the sensor network, a link to a higher node may be lost due to node movement or loss of function. In FIG. 6A, a phenomenon in which a link with node c which is an upper node of node e is disconnected corresponds to this phenomenon.

When the link with the higher node on the routing tree is lost in this way, the node determines whether there is another replaceable higher node (step 500). If there is another replaceable higher node, it can be replaced by the higher node, so the path can be recovered.

In the example shown in FIG. 6, node e cannot recover the path by node replacement since there is no replaceable parent node other than node c.

If there is no substitute upper node, a link error packet is generated and the routing length setting unit changes the routing length to the maximum value of the settable routing length (step 502). As in the above-described embodiment, when 1 byte is allocated to the routing length, the maximum value of the routing length is 255. The link error packet is a packet indicating that the link is lost, and the link error packet includes changed routing length information.

The generated link error packet is broadcast to neighboring nodes (step 504).

The node that received the broadcasted link error packet is in one of two states. The node receiving the link error packet may also be in a lost link or a maintained state. If the link is lost, the routing length is set to its maximum value.

The node receiving the link error packet determines whether its routing length is less than the routing length included in the LER (step 506).

 If the node receiving the link error packet is a node whose link is not lost, the routing length is smaller than the routing length set in the link error packet. If the routing length of the node that received the link error packet is less than the routing length of the link error packet (that is, not the node that lost the link), the node that receives the link error packet generates a sync packet and sends it to the link loss node. (Step 512).

The link lost node receiving the sync packet sets its routing length to increase by 1 compared to the node transmitting the sync packet using the information included in the sync packet, and sets the node transmitting the sync packet as its parent node. To recover the path (step 514).

On the other hand, if the routing length of the node receiving the link error packet is not smaller than the routing length of the link error packet (that is, the node receiving the link error packet is also the node that lost the link), the node receiving the link error packet is also A link error packet is generated and broadcast to the neighbor node (step 508).

In this case, the node receiving the link error packet receives the synchronization packet generated from another node (i.e., generated from the node that has not lost the link) (step 510), and passes its path through the received synchronization packet. Recover and send a sync packet to the link lost node (step 512), and a path recovery procedure using the sync packet may proceed (step 514).

In FIG. 6B, when node e loses the link due to node c's malfunction, node e broadcasts a link error packet. On the other hand, due to the loss of the link of the node e, the nodes g, i, j are also in the lost link state. Therefore, the nodes g, i, and j receiving the link error packet also broadcast the link error packet to the neighbor node, and the routing length is set to 255, which is the maximum value.

Node h, whose link is not lost, sends a sync packet to node i when it receives the link loss packet.

As shown in (c) of FIG. 6, the paths of the lost nodes are restored while delivering the synchronization packet generated from the node h, and the routing length (hop count) is determined by the routing length of the node h that transmitted the synchronization packet. Incremented one by one.

Hereinafter, a data transmission method will be described after a synchronization and routing path between nodes is established using a synchronization packet.

FIG. 7 is a diagram illustrating a data transmission scheme in a conventional S-MAC protocol, and FIG. 8 is a diagram illustrating a data transmission scheme according to an embodiment of the present invention. 7 and 8 illustrate a process in which data is transmitted from node 1 to node 4.

Referring to FIG. 7, in the conventional S-MAC protocol, node 1 transmits a ready to send (RTS) packet to node 2 when transmitting data to node 2, and node 2 transmits a clear to send (CTS) packet to node 1. After transmitting to the data transmission and reception process is performed. Node 3 may overhear the CTS packet transmitted by Node 2 but does not respond to it.

When data transmission and reception is completed, the node 2 transmits an ACK packet to the node 1 indicating that data reception is completed. The data transmission and reception between the node 2 and the node 3 is performed in the same manner as the data transmission and reception between the node 1 and the node 2, and also in the case of the data communication between the node 3 and the node 4.

At this time, the node 4 repeats the active state and the sleep state in accordance with the synchronization set in the synchronization step.

Such a conventional S-MAC method always has to exchange RTS packets and CTS packets between nodes, and there is a problem of energy inefficiency by repeatedly activating and deactivating states even in a state of not transmitting or receiving data.

Referring to FIG. 8, data transmission and reception between Node 1 and Node 2, which are nodes that initially transmit data, is performed in the same manner as in the conventional S-MAC. However, when the node 3 overhears the CTS packet of the node 2, the node 3 transmits a Preoccupancy Ready To Send (PRTS) packet to the next node, Node 4. The PRTS packet includes basic information for calculating the time that Node 4 can remain in sleep until Node 4 starts receiving data, and Node 4 receiving the PRTS packet uses the basic information included in the PRTS packet. To calculate the deactivation time and enter the deactivation state for the calculated time.

On the other hand, Node 3, which overhears the CTS packet of Node 2, overhears the ACK packet of Node 2, and Node 2 does not provide a separate RTS packet to Node 3, and Node 3 provides the CTS packet directly to Node 2 Data transmission and reception is performed between node 2 and node 3.

In addition, after waking from the inactive state, node 4 transmits a CTS packet to node 3 to initiate data transmission and reception with node 3.

Such a data transmission method of the present invention has an advantage of minimizing unnecessary transmission of RTS packets. In addition, by the PRTS packet, the node that receives the PRTS packet can remain inactive until data transmission / reception is performed, which is advantageous in terms of energy efficiency and solves a delay problem due to duty cycle in a multi-hop data transmission environment.

Although the above has been described with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified and modified within the scope of the present invention without departing from the spirit and scope of the present invention described in the claims below. It will be appreciated that it can be changed.

1 is a diagram illustrating a field configuration of a sync packet according to an embodiment of the present invention.

2 is a flowchart illustrating a process of forming a routing tree by determining a higher node of a specific node of a network.

3 is a diagram showing an example of a routing tree structure formed by routing setting using a synchronization packet according to an embodiment of the present invention.

4 is a block diagram showing a configuration of a network node to which a cross-layer based routing configuration according to the present invention is applied.

FIG. 5 is a flowchart illustrating a procedure for recovering a path when a link is lost due to movement or loss of function of a node according to an embodiment of the present invention.

6 is an exemplary diagram illustrating a process of restoring a path in a routing tree.

7 is a diagram illustrating a data transmission scheme in a conventional general S-MAC protocol.

8 illustrates a data transmission scheme according to an embodiment of the present invention.

Claims (12)

(A) receiving a synchronization packet from neighboring nodes, the synchronization packet comprising a routing length corresponding to a hop count with a sink node and a routing cost corresponding to the node's energy efficiency; Checking routing length information included in the received synchronization packets and selecting a node having the smallest routing length as an upper node; In step (b), if the number of nodes having the shortest routing length is plural, step (c) as an upper node for selecting a node having the smallest routing cost; And (D) setting a routing length to be increased by 1 than the selected node, calculating and setting a routing cost of the node itself, and broadcasting a synchronization packet including the set routing length and the routing cost to neighboring nodes. But If a link error packet is received from another node, if the link error packet is not in the link loss state, a sync packet including the routing length and the routing cost is transmitted to the node transmitting the link error packet; Cross layer-based routing and data transmission method in a wireless sensor network, characterized in that for broadcasting. The method of claim 1, The other node receiving the synchronization packet broadcast in step (d) repeats steps (a) to (d) to form a routing tree structure in the synchronization step. Routing and data transfer method. The method of claim 1, The routing cost (r_cst) is calculated by the following equation using the unit data transmission cost (C _T ) and the energy cost (C _E ) of the node corresponding to the initial energy and remaining energy ratio of the node. Cross-layer based routing and data transmission method in wireless sensor networks.

In the above equation, α and β are weights having a value between 0 and 1, including 0 and 1. The method of claim 1, If a link with an upper node is lost, setting a routing length to a maximum value and broadcasting a link error packet including the set routing length; And Receiving a sync packet from a neighbor node, rerouting using a routing length included in the sync packet and information of the neighbor node, the cross-layer based routing in a wireless sensor network, and Data transfer method. delete The method of claim 1, When overhearing a CTS (Clear To Send) packet from a lower node, transmitting a Preoccupied Ready To Send (PRTS) packet to a higher node;-time at which the upper node maintains a sleep state in the PRTS packet Contains basic information to determine In case of overhearing the ACK packet from the lower node, transmitting a CTS packet to the lower node to initiate data transmission and reception with the lower node, The upper node determines the deactivation time by using the basic information, and maintains the deactivation state for the determined time period. The method of claim 6, When the deactivation state of the upper node is terminated, receiving and transmitting data to and from the upper node by receiving a CTS packet from the upper node further cross-based routing and data transmission in the wireless sensor network, characterized in that Way. A node device for configuring a network for cross-layer routing and data transmission in a wireless sensor network, A sync packet receiver for receiving sync packets transmitted from other nodes and including a routing length corresponding to a hop count with a sink node and a routing cost corresponding to a node's energy efficiency; A routing path setting unit which selects an upper node using the routing length and the routing cost; A routing length setting unit configured to increase a routing length by one as compared with the selected upper node; A routing cost setting unit configured to calculate a routing cost using a unit data transmission cost C _T and an energy cost C _E of the node corresponding to the initial energy and remaining energy ratio of the node; A synchronization packet transmitter configured to broadcast a synchronization packet including a routing length set in the routing length setting unit and a routing cost set in the routing cost setting unit to neighbor nodes, When receiving a link error packet from another node, the synchronization packet transmitter transmits a synchronization packet including the routing length and a routing cost to a node that has transmitted the link error packet. Broadcasting link error packets to a node Node device constituting the network for cross-layer based routing and data transmission in a wireless sensor network characterized in that. The method of claim 8, The routing path setting unit checks the routing length information included in the received synchronization packets, selects the node having the smallest routing length as an upper node, and when the number of nodes having the shortest routing length is plural, the node having the smallest routing cost. The node device constituting the network for cross-layer-based routing and data transmission in the wireless sensor network, characterized in that for selecting the upper node. In the data transmission method in a wireless sensor network, When overhearing a Clear To Send (CTS) packet from a lower node, transmitting a Preoccupied Ready To Send (PRTS) packet to a higher node; Contains basic information to determine In case of overhearing the ACK packet from the lower node, transmitting a CTS packet to the lower node to initiate data transmission and reception with the lower node, The upper node determines the deactivation time using the basic information, and maintains the deactivation state for the determined time. The method of claim 10, When the deactivation state of the upper node is terminated, receiving a CTS packet from the upper node and performing data transmission and reception with the upper node further comprising a data transmission method in a wireless sensor network. The method of claim 11, And transmitting the RTS packet to the upper node before transmitting and receiving data to and from the upper node.

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