KR20120063265A - An efficient routing system basee on link quality and load balancing for wireless sensor networks - Google Patents

Abstract

PURPOSE: An effective routing method and apparatus thereof are provided to register a sensor node in a network by selecting a parent node by using metrics instead of RSSI(Received Signal Strength Indicator) signal strength. CONSTITUTION: A calculation unit calculates transmission costs of neighbor wireless sensor nodes from wireless sensor nodes. A selecting unit selects the neighbor wireless sensor node corresponding to the lowest transmission cost in the neighbor sensor nodes. A communication unit communicates with a sync node which passes through the selected neighbor wireless sensor node. The transmission costs include a function relationship with traffic loads of the neighbor wireless sensor nodes corresponding to the transmission costs.

Description

Effective Routing Method and Device Using Link Status and Traffic Distribution Information in Wireless Sensor Networks {AN EFFICIENT ROUTING SYSTEM

The present invention relates to a routing technique in a wireless sensor network, and more particularly, to a routing method using link state and traffic distribution information in a wireless sensor network for presenting a new metric using link quality and traffic volume information for load distribution. It is about.

Demand for energy-efficient user space wireless sensor networks (WPANs) is needed to effectively perform farming, natural disaster monitoring, 3D games, network-based toys, industrial equipment, welfare for the elderly, and environmental monitoring in the near future. It is increasing. For these applications, there is a need for small embedded systems that operate in a wireless environment with limited battery power. Compared with the existing wired network, the wireless sensor network requires excellent throughput and relatively low data rate. Wireless sensor nodes require extremely low power consumption due to their external or human installation.

In the WPAN environment, IEEE 802.15.4 offers very low battery power consumption and excellent price competitiveness compared to the Bluetooth standard. It defines standards for the Physical Layer (PHY) and Medium Access Control (MAC) that can be compatible with and interoperate with existing IEEE 802 standards. The network and upper layers are designed for compatibility between existing WPAN devices. Follow the formed ZigBee federation standard. The MAC layer plays a very important role in WPAN in terms of energy saving and efficient resource sharing. The relationship between the IEEE 802.15.4 and ZigBee federations is similar to that between the existing IEEE 802.11 and WiFi federations. Recently, the IEEE 802.15.4-based ZigBee alliance is still in the process of modifying the higher layer standards.

Many routing protocols for wireless sensor networks have been studied. These studies can be divided into four groups as follows. That is, minimum hop routing, minimum energy routing, load balancing routing, and geographical routing. Here, the minimum hop routing is a method of selecting a path capable of minimizing hops required to reach the sink node. The minimum energy routing method selects a source node and a sink node path that can minimize energy consumption in consideration of a relationship between energy required for data packet transmission and a transmission distance. The load-balancing routing method selects a route that can distribute traffic across as many nodes as possible, even if the selected route is not the optimal one in terms of energy consumption. The geographic routing method is to obtain the location information of the final destination and neighbor nodes and then deliver the packet to the node located closer to the final destination than the location of the node having the data packet to be transmitted. ZigBee prefers Tree Routing, which can be routed using simple but limited resources. Tree routing transfers data from sensor nodes to sink nodes based on parent-child relationships created during the topology formation of the IEEE 802.15.4 MAC (MAC) layer. However, the tree routing method can result in poor network performance and node lifetime due to non-optimal path selection, congestion, and uneven traffic distribution. That is, the tree routing method transmits data from the wireless sensor node to the sink node based on the parent-child relationship created during the topology formation of the MAC layer, so that the new wireless sensor node can join the network. Since a node having a strong RSSI signal is selected as a parent node, there is a problem in that traffic is not distributed. In addition, in the tree routing, the node having the strongest Received Signal Strength Indicator (RSSI) signal is selected as the parent node so that the new node joins the network. Therefore, traffic is not distributed, so some nodes transmit a large amount of traffic and energy is quickly depleted.

Accordingly, in the related art, to solve this problem, a new metric that uses link quality and traffic volume information for load balancing is proposed, and a parent node is selected to join the network by using the suggested metric instead of RSSI signal strength. Development of technology is required. In addition, by using an alternatively proposed cost function based routing (CFR) method, there is a demand for technology development to always maintain good performance regardless of the SO (Superframe Order) value compared to the tree routing method.

The technical problem to be solved by the disclosed technology is to provide a method and apparatus using the link state and traffic distribution information in a wireless sensor network for presenting a new metric using the link quality and traffic volume information for load distribution.

A first aspect of the disclosed technology to achieve the technical problem is a routing method of a wireless sensor network comprising a sync node and a plurality of wireless sensor nodes, (a) a new wireless sensor node newly participating in the wireless sensor network; Are transmission costs of one or more neighboring wireless sensor nodes among the plurality of wireless sensor nodes, wherein each of the transmission costs is a traffic amount of a neighboring wireless sensor node corresponding to the respective transmission cost of the neighboring wireless sensor nodes. calculating a proportional to a traffic load and inversely proportional to a link quality between the new wireless sensor node and the neighboring wireless sensor node; (b) the new radio sensor node selecting a neighbor radio sensor node corresponding to the lowest transmission cost among the transmission costs among the neighbor radio sensor nodes; And (c) the new wireless sensor node communicating with the sink node via the selected neighbor wireless sensor node.

A second aspect of the disclosed technology to achieve the technical problem is a routing device of a wireless sensor network comprising a sync node and a plurality of wireless sensor nodes, the new wireless sensor node newly participating in the wireless sensor network Transmission costs of one or more neighboring wireless sensor nodes among the wireless sensor nodes of the wireless node, wherein each of the transmission costs is a traffic load of the neighboring wireless sensor node corresponding to the respective transmission cost of the neighboring wireless sensor nodes. Calculating unit for calculating a function relation; A selection unit for the new wireless sensor node to select a neighboring wireless sensor node corresponding to the lowest transmission cost among the transmission costs among the neighboring wireless sensor nodes; And a communication unit in which the new wireless sensor node communicates with the sink node via the selected neighboring wireless sensor node.

Embodiments of the disclosed technology can have the effect of including the following advantages. However, the embodiments of the disclosed technology are not meant to include all of them, and thus the scope of the disclosed technology should not be understood as being limited thereto.

An effective routing method using link state and traffic distribution information in a wireless sensor network according to an embodiment of the present invention proposes a new metric using link quality and traffic amount information for load distribution.

In addition, an effective routing method using link state and traffic distribution information in a wireless sensor network according to another embodiment of the present invention proposes a method of joining a network by selecting a parent node using a metric instead of RSSI signal strength. .

In addition, the effective routing method using link state and traffic distribution information in the wireless sensor network according to another embodiment of the present invention, by using the CFR method to maintain a good performance regardless of the SO (Superframe Order) value at all times To provide.

1 is a view for explaining a beacon interval sharing principle of an effective routing method using link state and traffic distribution information in a wireless sensor network according to an embodiment of the present invention.
2 is a diagram illustrating a tree routing operation principle of an effective routing method using link state and traffic distribution information in a wireless sensor network according to an embodiment of the present invention.
3 is a view for explaining a node connection process of an effective routing method using link state and traffic distribution information in a wireless sensor network according to an embodiment of the present invention.
4 is a diagram illustrating a traffic table of the wireless sensor node 1 in an effective routing method using link state and traffic distribution information in the wireless sensor network according to the embodiment of the present invention.
5 is a diagram illustrating a method of determining a parent node among an effective routing method using link state and traffic distribution information in a wireless sensor network according to an embodiment of the present invention.
FIG. 6 is a diagram for describing a pseudo code of a cost value (Cost) configuration process of a beacon frame in an effective routing method using link state and traffic distribution information in a wireless sensor network according to an embodiment of the present invention.
FIG. 7 is a diagram illustrating a cost value (Cost) transmitted by each node through a beacon frame in an effective routing method using link state and traffic distribution information in a wireless sensor network according to an embodiment of the present invention.
FIG. 8 is a diagram illustrating a pseudo node selection process pseudo code in an effective routing method using link state and traffic distribution information in a wireless sensor network according to an embodiment of the present invention.
9 is a diagram illustrating parameters used in the simulation of an effective routing method using link state and traffic distribution information in a wireless sensor network according to an embodiment of the present invention.
10 is a diagram illustrating an example of changing a superframe order (SO) value after fixing a BO (Beacon Order) value in a duty cycle in an effective routing method using link state and traffic distribution information in a wireless sensor network according to an embodiment of the present invention. It is a graph for explaining the efficiency according to.
FIG. 11 is a view illustrating a transmission node of a transmission data packet according to a change of a SO (Superframe Order) value in a duty cycle in an effective routing method using link state and traffic distribution information in a wireless sensor network according to an embodiment of the present invention. It is a graph to explain the rate of reaching the Sink Node correctly.
12 is a graph showing the total amount of energy consumed when each node transmits a data packet according to a duty cycle in an effective routing method using link state and traffic distribution information in a wireless sensor network according to an embodiment of the present invention.

The description of the disclosed technique is merely an example for structural or functional explanation and the scope of the disclosed technology should not be construed as being limited by the embodiments described in the text. That is, the embodiments may be variously modified and may have various forms, and thus the scope of the disclosed technology should be understood to include equivalents capable of realizing the technical idea.

Meanwhile, the meaning of the terms described in the present application should be understood as follows. The terms 'first', 'second', etc. are used to distinguish one component from another component and the scope of rights should not be limited by these terms. For example, the first component may be named a second component, and similarly, the second component may also be named a first component.

When a component is referred to as being "connected" to another component, it should be understood that there may be other components in between, although it may be directly connected to the other component. On the other hand, when an element is referred to as being "directly connected" to another element, it should be understood that there are no other elements in between. On the other hand, other expressions describing the relationship between the components, such as "between" and "immediately between" or "neighboring to" and "directly neighboring to", should be interpreted as well.

Singular expressions should be understood to include plural expressions unless the context clearly indicates otherwise, and terms such as "include" or "have" refer to features, numbers, steps, operations, components, parts, or parts thereof described. It is to be understood that the combination is intended to be present, but not to exclude in advance the possibility of the presence or addition of one or more other features or numbers, steps, operations, components, parts or combinations thereof.

Each step may occur differently from the stated order unless the context clearly dictates the specific order. That is, each step may occur in the same order as specified, may be performed substantially simultaneously, or may be performed in the reverse order.

All terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the disclosed technology belongs, unless otherwise defined. Terms defined in commonly used dictionaries should be interpreted to be consistent with meaning in the context of the relevant art and can not be construed as having ideal or overly formal meaning unless expressly defined in the present application.

1 is a view for explaining a beacon interval sharing principle of an effective routing method using link state and traffic distribution information in a wireless sensor network according to an embodiment of the present invention. Referring to FIG. 1, MAC (MAC) protocols currently widely used in wireless sensor networks are largely classified into a time division multiple access (TDMA) method and a carrier sense multiple access (CSMA) method. TDMA is a method in which a sink node allocates time slots to each node according to resource occupancy so that each sensor node transmits an uplink / downlink data packet. In contrast, the CSMA method uses a resource sharing algorithm according to a random backoff and a contention window based on contention. At present, WPAN is developing a MAC standard in IEEE 802.15.4 that can accommodate both TDMA and CSMA methods. In addition, the ZigBee Alliance is available at the network layer as a vendor standard. The super frame structure proposed in relation to standardization in IEEE 802.15.4 can be classified into a time division beacon (TDB) and a shared beacon (Beacon-Only Period, BOP).

The present invention proposes an efficient routing protocol using a shared beacon scheme as shown in FIG. In the shared beacon section, node ZR0, which is a fan coordinator, is B1, node ZR1, which is a child coordinator, node B2, and node ZR2, which is a grandchild coordinator, is B3. B1, B2, and B3 are divided into guard intervals.

On the other hand, one superframe of IEEE 802.15.4 is divided into a superinterval (SD) section by a BI (Beacon Interval) section and a SO (Superframe Order) section. In the SD (Superframe Duration) section, the active area is always divided into 16 slots regardless of the size of the BI (Beacon Interval). It is divided into only period, contention access period (CAP), and contention free period (CFP) / guaranteed time slot (GTS). The BOP (Beacon Only Period) section is a section for ZigBee Coordinator (ZC0) and ZigBee Routers (ZR1 to ZR2) to transmit beacons, regardless of CSMA. It means the interval to transmit. At this time, since several beacons are synchronized in one superframe, all devices in one WPAN network transmit / receive data using the same superframe structure.

2 is a diagram illustrating a tree routing operation principle of an effective routing method using link state and traffic distribution information in a wireless sensor network according to an embodiment of the present invention. 3 is a view for explaining a node connection process of an effective routing method using link state and traffic distribution information in a wireless sensor network according to an embodiment of the present invention. 1 to 3, according to the IEEE 802.15.4 standard, as shown in FIG. 1, a wireless sensor node receiving a beacon in a BOP section needs an association operation to share network resources.

First, the wireless sensor node ZR1 uses the association request information generated in the MAC layer to connect to the wireless sensor node ZR0. 4, 5, 6, 7, and 8) to use a tree routing method for establishing an efficient packet transmission path from the sink node (Sink Node: 0).

According to the IEEE 802.15.4 standard, wireless sensor nodes (ZR) require an association request before transmitting a packet in the WPAN. This connection is basically made through sharing control information between a parent node (ZR0) and a child node (ZR1) as shown in FIG. 2. At this time, each child node (eg, ZR1 or / and ZR2) may know the address of the parent node (eg, ZR0) at the time of connection.

In this case, it is necessary to create a connection structure between the wireless sensor node and the sink node by using an association tree between the parent node and the child node, and to communicate using the connection node. Cross-layer tree routing. According to the research results, when the wireless sensor node (ZR1) is connected to the wireless sensor node (ZR0), it subscribes using simple link characteristics such as RSSI or ED (Energy Detection) scan. In this method, there is a lot of problems in selecting an optimal path with the existing method of performing a subscription considering only a simple RSSI in an environment where there is a large difference between the surrounding load and the RSSI.

Accordingly, in the present invention, an efficient packet transmission path from a wireless sensor node (1, 2, 3, 4, 5, 6, 7 or 8 in FIG. 3) to a sink node in consideration of the costs of neighboring nodes in the network layer. Present how to set up. In detail, the optimal path is determined by considering the cost of the neighbor RSSI and the traffic distribution information based on the BOP section and the tree routing.

Referring to Figure 3, looks at the process of connecting the new wireless sensor node 6 to the network. According to the IEEE 802.15.4 standard, the new wireless sensor node 6 goes through a connection step to access the network. At this time, the new wireless sensor node 6 performs a scanning process to discover neighboring wireless sensor nodes (at least one of 0, 1, 2, 3, 4, 5, 7, 8) and has the strongest RSSI node. Connect to parent node by selecting as parent node. However, the conventional method does not consider the traffic load of the wireless sensor nodes at all, and load balancing is not performed in terms of the entire network because only the parent node is determined and connected according to the RSSI signal strength.

Thus, as shown in Figure 3, shows a new wireless sensor node 6 is connected to the network. As shown, it is assumed that the new wireless sensor node 6 is a new node and receives beacon frames from the wireless sensor node 4 and the wireless sensor node 2 which are neighboring wireless sensor nodes. It is also assumed that the signal from the neighboring wireless sensor node 4 is stronger than the signal from the neighboring wireless sensor node 2. According to the conventional IEEE 802.15.4 standard method, the neighbor wireless sensor node 4 having the strong RSSI signal will be selected and connected. Then, the data transmitted by the new wireless sensor node 6 has to compete with data transmitted by the wireless sensor nodes 1, 3, 4, 7, and 8 in the process of transmitting to the sink node (0). Since the right side of the sink node (0) is only competing with the wireless sensor nodes (2) and (5), it causes an imbalance in traffic distribution. Therefore, in consideration of traffic distribution, it is more advantageous to connect the new wireless sensor node 6 with the neighboring wireless sensor node 2.

Therefore, it is not efficient to consider only traffic distribution in the connection step of the conventional novel wireless sensor node 6. This is because the performance of the wireless sensor network is greatly affected by the link quality of the radio channel. Accordingly, the present invention proposes a method of determining a traffic transmission cost (value), which is a new metric in consideration of traffic load (TL) and link quality (LQ), and determining which node to connect to accordingly. Suggest.

Meanwhile, in the present invention, it is assumed that the amount of traffic to be transmitted by the wireless sensor nodes is not variable and is known in the step of connecting to the network. In general communication, the larger the traffic amount value (TR) and the lower the link quality value (LQ), the higher the cost for data transmission. Therefore, the "coast function" for calculating the cost value Cost used in the present invention is defined as in Equation 1 below.

Here, the link quality value (LQ) of the radio channel is calculated based on the RSSI. The RSSI value is represented by 1 byte and has an integer value between 0 and 255. On the other hand, there is no Vendor product that represents 256 signal strength levels. That is, the maximum RSSI (RSSI _max ) receivable by the wireless sensor node is selected and used. Therefore, the RF (Radio Frequency) energy level of a product made by one vendor has a value ranging from 0 to RSSI _max .

In the present invention, the link quality value (LQ) is a value obtained by dividing the RSSI value of the received packet by RSSI _max without using the RSSI value itself as a value so that it can be compared with each other regardless of a vendor's product. That is, it is expressed as following Equation 2.

Here, RSSI _receive is an RSSI value measured when a packet is received by a wireless sensor node to which a new wireless sensor node is to be connected. Since RSSI values change dynamically over time, use the average of the values obtained over time. In general, when the link quality value (LQ) is about 0.2, it means the roaming limit value. If the link quality value (LQ) is about 0.1 or less, it is considered that no signal is being transmitted on the link channel. Therefore, in order for the new wireless sensor node 6 to connect to the network and operate normally, the value must be 0.3 or more. Also, in order to calculate the cost value, each wireless sensor node must have a traffic amount value TR, which is traffic information. More specifically, each wireless sensor node maintains a traffic table for traffic information. The traffic table is a "child node ID" so that you can see how much traffic is passing through which child nodes, and "child nodes" that send traffic through child nodes. Three pieces of information are included: "layer node ID" and "traffic quantity value" of the lower layer node. Meanwhile, the traffic table may also include traffic information about child nodes.

Table 1 of FIG. 4 shows a traffic table of the neighbor wireless sensor node 1 in FIG. The traffic amount value TR _i refers to a traffic amount value generated by the neighboring wireless sensor node i and transmitted to a sink node (0). For clarity, it is assumed that each wireless sensor node transmits to a sink node (0) by generating a certain amount of traffic.

Meanwhile, the new wireless sensor node j decides which node to connect with by a method to be described later, and then transfers its traffic amount TR _i to the parent node through an association request message. do. The parent node then records this information in its own traffic table and sends a connection request message back to its parent node so that it can update the traffic table.

The process continues until the connection request message reaches a sink node (0). Through this, the sink node (0) can know the traffic information of all nodes connected to the network. Each wireless sensor node periodically transmits to the child node including cost information in its beacon frame.

The format associated with the cost value Cost in the beacon frame is composed of two parts, parent node information (A) and child node information (B), as shown in FIG. The length of the child node information (B) portion depends on the number of child nodes each node has.

In FIG. 5, "PID" is an ID of a parent node, and "CID" is an ID of a child node. The child node ID CID is used to inform which child node the cost value Cost included in the beacon frame is. The neighboring wireless sensor node i that receives the beacon frame from the parent node configures a beacon frame to be transmitted as follows. The "PID" of the parent node information part is its ID (i), and the cost value (Cost) is the child node information part of the beacon frame transmitted by its parent node (Parent Node). It is set to the cost value Cost _i transmitted to its node ID. &Quot; CID " of the child node information portion is j, which is its own child node, and its cost value Cost _i is given by Equation 3 below.

Here, the cost value Cost _{i, j} is the traffic TR _{i, j} that the neighboring wireless sensor node i will receive through the new wireless node j, the wireless sensor node i, and the wireless sensor node j. Means a cost value Cost, which is wired by Equation 1, using the link quality value LQ measured in the inter-) communication. The traffic amount values TR _{i and j} are the sum of the traffic amount value TR _j of the new wireless sensor node j and the traffic amount value TR _k of the child node k of the new wireless sensor node j.

According to one embodiment, the traffic that the wireless sensor node 1 will receive from the child node 3 in FIG. 3 is TR _{1 , 3} = TR ₃ + TR ₇ + TR ₈ . The traffic amount TR to be received from each child node is obtained through the traffic table maintained by the child node. If the calculated cost value is not an integer, it is rounded up and expressed as an integer for convenience of expression. If there is no child node because it is the last node, only the parent node information is included in the beacon frame and transmitted.

6 illustrates a process of configuring cost information of a beacon frame according to an embodiment.

As described above, the cumulative value of adding the cost value Cost included in the beacon frame to the cost value Cost of the lower layer node instead of the cost value Cost transmitted through each link is as follows. . When a new wireless sensor node attempts to connect to the network, it is necessary to know cost information transmitted on each link in the path from parent node to sink node to distribute traffic optimally. Can be selected. When the cost information (Cost) information for all links are carried in a beacon frame and transmitted, the amount of information increases, so that the accumulated information can be used to easily know the traffic state of the path.

On the other hand, an embodiment of the operation process is as follows. In FIG. 3, except for the Sink Node (0), the traffic amount value TR of each wireless sensor node is 10, the link quality value LQ of all links is 1, and the wireless sensor node 6 is still in the network. Assume that no. Referring to FIG. 7, which shows an example of a cost value included in a beacon frame transmitted by each wireless sensor node, the sink node 0 has a parent node of the beacon frame because no parent node exists. In the information part of a node, its node ID and cost value '0' are set as (0, 0), and the information part of the child node is a child node ID and each child node. Calculate and transmit the corresponding cost value Cost. Through the traffic table maintained by the sink node (0), the amount of traffic to be received from the child node (1) (TR _{0 , 1} = TR ₁ + TR ₃ + TR ₄ + TR ₇ + TR ₈ = 50) is received. The cost value Cost is calculated according to Equation 1 using the traffic amount value LQ obtained by measuring while communicating with the child node 1. The cost value Cost for the child node 2 is also calculated in this manner. According to the calculation result, the sink node (0) sends information (0, 0), (1, 50), and (2, 20) to child nodes of the wireless sensor node 1 and the wireless sensor node through the beacon frame. To 2). The node 1 and the node 2 receiving the beacon frame configure and transmit their beacon frame. The wireless sensor node 1 first fills the parent node information part using the cost value Cost ₁ transmitted from the child node information part included in the beacon frame received from its parent node 0 to its node ID. . That is, (0, 50). Subsequently, the amount of traffic to be received from each child node through its traffic table is obtained, and the cost value Cost for each child node is calculated using the traffic amount value LQ. That is, the child node (3) and child node (4) Cost value (Cost _1,3) and the cost value (Cost _1,4) on each of which is 30 and 10. Accordingly, the node 1 adds the cost value received from the sink node 0, which is the parent node, and the cost value Cost for each child node calculated by the node 1, and adds the child node information portion of the beacon frame. Fill it. That is, (3, 80) and (4, 60).

Finally, the wireless sensor node 1 transmits the filled parent node information part and child node information part in a beacon frame. That is, (0, 50), (3, 80) and (4, 60) are transmitted. The node receiving the beacon frame from the parent node performs the same process. In FIG. 7, since nodes 4, 5, 7, and 8 do not have child nodes, only the parent node information part is included in the beacon frame and transmitted as follows. Thus, as shown, node 4 is (1, 60), node 5 is (2, 30), node 7 is (3, 90), and node 8 is (3, 90). )

On the other hand, the new wireless sensor node 6 which wants to connect to the network is obtained by using the cost value Cost of the parent node information part included in the beacon frame received from the neighbor node and the RSSI value measured when the beacon frame is received. Based on the traffic quantity value (LQ), it determines which neighbor wireless sensor node is a parent node and determines whether to perform a connection. In the present invention, the new wireless sensor node 6 determines a neighboring wireless sensor node having a minimum cost value Cost as a parent node as shown in Equation 4 below.

Here, N denotes a set of neighbor nodes of the new node, Cost value Cost _i is a cost value of the parent node information part included in the beacon frame received from the neighbor wireless sensor node i, and Cost a _{i, j} is a new wireless sensor node (j) traffic yanggap (TR _j) and a neighboring wireless sensor node the traffic yanggap (LQ) calculated on the basis of the RSSI value measured when the beacon frame received from (i) in the equation (1) It is the value obtained by substitution.

According to one embodiment, in FIG. 3, the wireless sensor node 6 wants to connect to the network and receives a beacon frame from the wireless sensor node 2 and the wireless sensor node 4, and the traffic volume value LQ is respectively. Assume 0.8 and 1 In addition, it is assumed that the traffic amount value TR ₆ of the new wireless sensor node 6 is 10, and the cost value Cost received from the neighboring wireless sensor node is as shown in FIG. The cost value (Cost _2,6 ) between the neighboring wireless sensor node 2 and the neighboring wireless sensor node 6 is 13 (= 10 / 0.8) and between the neighboring wireless sensor node 4 and the neighboring wireless sensor node 6. The cost value Cost _4,6 of 10 is 10 (= _10/1 ). Considering the value of the parent node information portion of the neighboring wireless sensor node, the cost is 33 (= Cost ₂ + Cost _{2 , 6} = 20 + 13) when connected to the neighboring wireless sensor node (2), and the neighboring wireless sensor node (4). ) Is 70 (= Cost ₄ + Cost _{4 , 6} = 60 + 10), so the new node determines the neighboring wireless sensor node 2 as its parent node.

To verify the effectiveness of the proposed CFR protocol, CFR and Tree Routing (TR) are implemented in TOSSIM environment, a simulator for TinyOS. The tested network configuration is shown in Figure 3 and the total number of nodes is nine. Adjacent nodes were placed in radio frequency coverage. The configured nodes are arranged at regular intervals, and each node forms a beacon-based IEEE 802.15.4 network composed of full-function device (FFD) nodes with routing functions. The parameters used in the simulation are shown in Table 2 of FIG. 9. Each node generates data at the constant bit rate (CBR).

On the other hand, the performance evaluation elements used in the present invention are as follows.

First, consider a delivery rate indicating a ratio of packets that accurately reach a sink node among data packets transmitted by each wireless sensor node. Second, consider the throughput that represents the amount of data received by the sink node without error. Finally, consider the energy that represents the total amount of energy consumed by nodes on the network to transmit data packets.

FIG. 10 shows the efficiency when the SO (Superframe Order) value is changed from 4 to 8 after fixing the BO (Beacon Order) value to 8 in the duty cycle. As shown in the results, as the SO (Superframe Order) value increases, the efficiency of both tree routing (TR) and CFR increases. This is because when the SO (Superframe Order) value is increased, each node is in the operation mode longer than the time in the sleep mode, so that a large amount of data can be transmitted to the sink node.

The proposed method shows that the efficiency is more effective than tree routing regardless of the change of SO (Superframe Order) value. Tree routing does not distribute the traffic because the parent child relationship is formed by the RSSI value, and much traffic is transmitted along the same path, causing competition and collision for channel occupancy. However, since the proposed CFR method distributes traffic based on the cost function of Equation 1, competition and collision are relatively reduced, thereby improving performance.

FIG. 11 illustrates a rate at which a transmission data packet reaches a sink node accurately according to a change in a superframe order (SO) value in a duty cycle. As shown in FIG. 10, since the proposed method distributes traffic using the cost function of Equation 1, it can be seen that there is a high possibility of successfully delivering a packet to a sink node. The tree routing method causes the inter-flow problem and the intra-flow problem more because of the undistributed traffic. Therefore, the transmission rate is low because they compete to transmit data with each other.

FIG. 12 shows the total amount of energy consumed by each node in transmitting data packets according to the duty cycle. As shown in FIGS. 10 and 11, as the SO (Superframe Order) value increases, the time for the node to be in the operation mode increases, so that efficiency and transmission rate also increase. As data packets transmitted in this way increase, energy consumed also increases. However, the proposed method consumes less energy than the tree routing method because traffic distribution reduces interflow and intraflow problems and reduces collisions.

The present invention can also be embodied as computer-readable codes on a computer-readable recording medium. Computer-readable recording media include all kinds of recording devices that store data that can be read by a computer system.

Examples of computer-readable recording media include ROM, RAM, CD-ROM, magnetic tape, floppy disks, optical data storage devices, and the like, which are also implemented in the form of carrier waves (eg, transmission over the Internet). It also includes.

The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion. And functional programs, codes and code segments for implementing the present invention can be easily inferred by programmers in the art to which the present invention belongs.

The disclosed method and apparatus have been described with reference to the embodiments illustrated in the drawings for ease of understanding, but these are merely exemplary, and various modifications and equivalent other embodiments are possible to those skilled in the art. Will understand. Therefore, the true technical protection scope of the disclosed technology should be defined by the appended claims.

0: sink node
1, 2, 3, 4, 5, 6, 7, 8: Wireless Sensor Node

Claims (9)

In the routing method of a wireless sensor network comprising a sync node and a plurality of wireless sensor nodes,
(a) Transmission costs of one or more neighboring wireless sensor nodes of the plurality of wireless sensor nodes, the new wireless sensor node newly participating in the wireless sensor network-each of the transmission costs is the neighboring wireless sensor nodes Calculating proportional to a traffic load of a neighboring wireless sensor node corresponding to each transmission cost, and inversely proportional to a link quality between the new wireless sensor node and the neighboring wireless sensor node;
(b) the new radio sensor node selecting a neighbor radio sensor node corresponding to the lowest transmission cost among the transmission costs among the neighbor radio sensor nodes; And
(c) the new wireless sensor node communicating with the sink node via the selected neighbor wireless sensor node. The method of claim 1,
A routing method in which the link quality is proportional to an RSSI _receive value, provided that RSSI _receive is an RSSI value measured when a packet is received by a neighboring wireless sensor node. The method of claim 1,
The link quality is RSSI _receive The routing method is proportional to the value divided by the RSSI _max value, wherein RSSI _receive is an RSSI value measured by the neighboring wireless sensor node when receiving a packet, and RSSI _max is a signal strength level that can be received by the neighboring wireless sensor node. Value) The method of claim 1,
The amount of traffic is received by the wireless sensor node constituting the wireless sensor network and how much traffic is transmitted from the lower layer wireless sensor node constituting the network, and each wireless sensor node constituting the wireless sensor network is connected to the network. A routing method including information on how much traffic is transmitted to a higher layer wireless sensor node. The method of claim 1,
The cost value of the new wireless sensor node is

Routing method performed by operation by. (If the neighboring wireless sensor node (i) and the new wireless sensor node (j), the cost _{i , j} is the neighboring wireless sensor node (i) through the new wireless sensor node (j) the traffic yanggap (TR _{i, j)} to receive neighbor search operation on the basis of the wireless sensor nodes (i) and the new wireless sensor node (j) a link quality value (LQ) measure in a communication between the cost _i is the The traffic amount value TR _i for the neighboring wireless sensor node i is calculated based on the link quality value LQ measured for the neighboring wireless sensor node i) The method according to claim 5, wherein the traffic amount value TR _{i, j} ,
And a traffic amount value TR _j of the new wireless sensor node j and a traffic amount value TR _k of a child node k of the new wireless sensor node j. The method of claim 1,
The new wireless sensor node

A routing method for determining a neighbor node having a minimum cost value Cost as a parent node. (Wherein N is the set of the neighboring wireless sensor nodes i of the new wireless sensor node j, and Cost _i is included in the beacon frame received from the neighboring wireless sensor node i). Cost _i Cost of the parent node information portion Cost _{i , j} is the cost _{i , j} is the traffic amount value TR _j of the new wireless sensor node j is measured when receiving a beacon frame from the neighboring wireless sensor node (i) Value obtained based on the traffic volume value (LQ) calculated based on the RSSI value) In the routing device of a wireless sensor network comprising a sync node and a plurality of wireless sensor nodes,
New wireless sensor nodes newly participating in the wireless sensor network transmit costs of one or more neighboring wireless sensor nodes among the plurality of wireless sensor nodes—each of the transmission costs is the respective one of the neighboring wireless sensor nodes. A calculation unit for calculating a traffic relation with a traffic load of a neighboring wireless sensor node corresponding to a transmission cost;
A selection unit for the new wireless sensor node to select a neighboring wireless sensor node corresponding to the lowest transmission cost among the transmission costs among the neighboring wireless sensor nodes; And
And a communication unit configured to communicate with the sink node by the new wireless sensor node via the selected neighbor wireless sensor node. The method of claim 8,
Wherein the functional relationship is proportional to the traffic load and inversely proportional to the link quality between the new wireless sensor node and the neighboring wireless sensor node.

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