KR101798065B1 - Wireless sensor network System to be available to redistribute connetion of node and method thereof - Google Patents

Abstract

According to an embodiment of the present invention, a wireless sensor network system capable of redistributing a connection node improves a throughput of data transmission. The wireless sensor network system is composed of a plurality of clusters, wherein each of the clusters includes one coordinator node and at least one sensor node. The wireless sensor network system further comprises a sink node which analyzes a traffic amount in each of the clusters and transmits a separating or joining command of the sensor node to a specific coordinator node among the coordinator node based on the analyzed result. The coordinator node receiving the command separates or joins the sensor node according to the separating or joining command of the sink node.

Description

Technical Field [0001] The present invention relates to a wireless sensor network system capable of redistributing access nodes, and a wireless sensor network system capable of redistributing connection nodes,

The present invention relates to a wireless sensor network. More particularly, the present invention relates to a technology for controlling the amount of traffic of each node when sensor nodes transmit data to a sink node. In order to provide reliability and timeliness of data transmission, And methods.

A wireless sensor network consists of several sensor nodes and one sink node. The reason for the congested traffic is that congested environment of convergence occurs when all the nodes are transmitted to the sink node. Second, congested environments can be created by the presence of congested areas or nodes. Such congestion causes problems such as buffer overflow, packet collision, packet loss, and the like, thereby reducing the reliability of the application. Therefore, in order to solve congestion, researches on data merging method, congested area detection and processing method and the like have been carried out.

    In the first case, the data merge method is a method of merging and collecting data from spatially close nodes when collecting data in a tree form in a wireless sensor network. This technique is designed in consideration of the fact that nodes with close spatial proximity are likely to collect similar data. This method has the merit that it can reduce the traffic by merging the data, but there is a problem that the reliability is low.

    Next, as a solution technique of the second case, the congestion area detection and processing technique increases the sensing period in order to solve the traffic in the congested area after detecting the congested area, reduces the amount of traffic by discarding the packet or blocks the routing to the congested area The traffic is bypassed and distributed. However, this method has a problem that accuracy and reliability of the sensing information are degraded because the sensing period is extended or the packet is discarded.

In order to solve the above-mentioned problem, the present invention is directed to a system and method for solving the above-mentioned problems, in which a command is issued to a coordinator constituting and operating each cluster to separate nodes included in a congested cluster, And the throughput of data transmission is improved by controlling the congestion degree of the wireless sensor network.

The objects of the present invention are not limited to the above-mentioned objects, and other objects not mentioned can be clearly understood by those skilled in the art from the following description.

According to an aspect of the present invention, there is provided a wireless sensor network system including a plurality of clusters each including a coordinator node and at least one sensor node, Further comprising a sink node for analyzing a traffic amount in each cluster and transmitting a separation or merging command of a sensor node to a specific coordinator node among the coordinator nodes based on the analysis result, wherein the coordinator node, Or the sensor node is separated or merged according to a joining command.

A wireless sensor network system capable of redistributing access nodes according to another aspect of the present invention is a wireless sensor network system including a plurality of clusters each including one coordinator node and one or more sensor nodes, And a sink node for transmitting a separation command of the sensor node to a specific coordinator node among the coordinator nodes based on the analysis result, wherein the coordinator node having received the command separates the corresponding sensor node according to the separation command of the sink node .

According to another aspect of the present invention, there is provided a connection redistribution method of a wireless sensor network system, including a plurality of clusters each including a coordinator node and at least one sensor node, and a sink node for collecting cluster information from the plurality of clusters, (1) receiving cluster information from the plurality of coordinator nodes and storing the received cluster information in a database, (2) receiving, from the received cluster information, the superframe of each cluster in a temporal (3) analyzing the stored cluster traffic information, (4) generating a sensor separation or joining command to the coordinator, (5) assigning a first cluster to the first coordinator, To detach the sensor node from the sensor node; and (6) instructing the two coordinators to join the sensor node to the second cluster.

According to the present invention, since congestion can be controlled by controlling the amount of transmission of all nodes, the overall packet loss rate can be minimized, thereby achieving reliability and timely communication in a wireless sensor network environment.

1 is a structural view of a wireless sensor network;
2 is a superframe structure diagram of a wireless sensor network;
FIG. 3 is an exemplary diagram illustrating a superframe scheduling of a cluster for congestion control according to an embodiment of the present invention; FIG.
4 is an exemplary diagram for explaining redistribution processing of an allocation channel according to the present invention;
5 is a configuration diagram of a wireless sensor network system capable of redistributing access nodes according to the present invention;
6 is a flow chart of a procedure of a connection redistribution method of a wireless sensor network system according to the present invention.
7 is a flowchart of a node redistribution method by traffic analysis according to the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In the present specification, the singular form includes plural forms unless otherwise specified in the specification. As used herein, the terms " comprises, " and / or "comprising" refer to the presence or absence of one or more other components, steps, operations, and / Or additions.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 shows a structure of a wireless sensor network.

A wireless sensor network (WSN) can be constructed using communication standards such as Wi-Fi (IEEE 802.11 and its downward compatibility) and Bluetooth (IEEE 802.15.4). Recently, Zigbee ), WirelessHART, and MiWi are designed and developed for the wireless sensor network (WSN). ZigBee, WirelessHart, and MaiWeb define a higher protocol stack that does not include the IEEE 802.15.4-2006 standard to provide a complete network solution.

The sink node 110 is a unit for identifying the wireless network system as a whole as a point connected to the external network. Generally, a class or a function designed to collect events arising from other objects or functions. In the field of wireless sensor networks, a base station transmitting data in a multi-hop environment base station.

The coordinator 120 manages a cluster constituting a part of a wireless network system, and a node where the coordinator 120 is located is called a coordinator node. There is one coordinator 120 in each cluster 140. The coordinator 120 uses the beacon signal to synchronize the sensor nodes in the cluster.

The coordinator 120 can separate the sensor nodes included in the cluster and join the sensor nodes that request the joining to the cluster to the cluster.

In addition, the coordinator 120 can allocate a data transmission interval of each sensor node 130 to a guaranteed time slot (GTS) included in the allocation interval of FIG. 2 in response to a data transmission request of the sensor nodes 130, And generates a cluster-specific superframe containing a data transmission schedule for all nodes in the cluster. That is, the coordinator determines whether to include the sensor node 130 in the cluster operated by the coordinator, and creates a data transmission schedule of all the sensor nodes 130 included in the cluster.

The sensor node 130 may be configured as a full-function device (FFD) or a reduced-function device on the standard document. However, the coordinator 120, which is a full function device (FFD), can not be the sensor node 130.

The router may function as a full function device (FFD), and the normal sensor node 130 corresponds to a restriction function device (RFD), but may also serve as a full function device (FFD).

1 may be any one of a star topology, a tree topology, a mesh topology, and a peer-to-peer topology, The invention is based on the premise of a wireless sensor network structure having a star structure or a tree structure because it is intended to enable reliable and timely communication by adjusting transmission schedules of sensor nodes belonging to each cluster. However, this is for redistributing traffic for scheduling between superframes, and actual data transmission and cluster configuration may be based on a mesh structure.

The cluster 140 includes one coordinator node 120 and one or more sensor nodes 130.

2 shows a superframe structure diagram of a wireless sensor network.

A beacon-enabled network superframe uses beacons to synchronize its time. The sink node 110 receives the beacon signal of the coordinator 120 and generates a schedule so that the activation periods of the superframes of the respective coordinators do not overlap in consideration of the size of the superframe.

For example, the sensing period may be set to be less than once per second, and the active period including the beacon may be less than or equal to 50 ms and less than or equal to 100 ms. The time slot may be within 1 ms.

The active portion is divided into a contention access period and a contention-free period. A time slot allocated to an allocation period is called a GTS (Guaranteed Time Slot). In the case of IEEE 802.15.4, the time slot is limited to 16 including the beacon, but the number limitation of the time slot need not be considered in the present invention. However, the terminology used and the use of each component can refer to the contents of IEEE 802.15.4 and ZigBee standard documents, but the scope of the present invention is not limited. For example, in the present invention, a contention period is divided into a first contention period and a second contention period. In FIG. 3, a contention interval following the beacon is referred to as a first contention interval, and a contention interval following the first contention interval is referred to as a second contention interval.

In the present invention, each sensor node 130 utilizes a first contention period as a period for requesting connection and data transmission to a coordinator included therein, and transmits a coordinator connection And a second contention period is used for an allocation request for data transmission.

The sensor nodes 130 included in the specific cluster request joining to the corresponding coordinator 120, and upon receiving a confirmation from the coordinator 120, the networking is completed and the data is transmitted using the allocation period.

3 is an exemplary diagram illustrating a superframe scheduling of a cluster for congestion control in a sink node according to an embodiment of the present invention.

Each sensor node locates the corresponding cluster, requests the coordinator that operates the cluster, and transmits the sensor information to the destination node in synchronization with the cluster when it receives the confirm request.

The sink node 110 schedules the transmission order for one or more clusters. The superframe information of the cluster is received from the coordinator 120, and a schedule is generated so that activation periods of superframes for each cluster are not overlapped in consideration of beacon synchronization information of each cluster. In FIG. 3, it can be confirmed that data is scheduled to be transmitted in order of cluster 1, cluster 2, and cluster 3.

4 is a diagram illustrating an allocation channel redistribution process according to the present invention.

As shown in FIG. 3, even if scheduling is performed for each cluster, traffic may be concentrated in a specific cluster. In this case, it is necessary to distribute the traffic by redistributing the nodes of the cluster.

Referring to FIG. 4, an allocation period for five sensor nodes A, B, C, D, and E is included in cluster 1 and an allocation period for one sensor node F is included in cluster 2. If the current situation is that traffic is concentrated in cluster 1, the sink node can move some of the sensor nodes in cluster 1 to cluster 2 and redistribute the entire traffic. For example, in the case of FIG. 4, two nodes (D, E) of cluster 1 can be moved to cluster 2.

When the sensor node is redistributed as shown in FIG. 4, the redistributed sensor node requests data transmission according to the second contention period timing of the cluster superframe to be joined, and the data transmission is performed in the next superframe of the cluster.

In FIG. 4, a cluster for separating the sensor node like the congested cluster 1 is referred to as a first cluster in the present invention. The cluster to join the separated nodes is referred to as a second cluster. The coordinator of the first cluster is referred to as a first coordinator, and the coordinator of the second cluster is referred to as a second coordinator. This is a definition for convenience of explanation, and the first coordinator and the second coordinator are not fixed.

5 is a block diagram of a wireless sensor network system capable of redistributing access nodes according to the present invention.

A wireless sensor network system capable of redistributing access nodes in the present invention includes a sink node 110 and one or more clusters 140 and a cluster 140 includes one coordinator 120 and one or more sensor nodes 130 do.

The sink node 110 stores the cluster information such as the traffic of the cluster, the node information generated from the initial sensor, and the superframe information of each cluster to construct a database.

The sink node 110 includes a CPU 500 that receives a data packet and transmits a command packet in a relationship between the WSN module 540 serving as an interface with the coordinator 120 and the WSN module 540, . The CPU 500 includes a storage unit for storing cluster information in a database, an analyzing unit for analyzing the traffic information of the cluster stored in the database, and an instruction generating unit for generating a command to be issued to the coordinator according to the analyzed result.

The WSN module 540 transmits a data packet containing cluster information to the CPU 500 and receives a command packet containing command information to be sent to the coordinator 120 from the CPU 500. The WSN module 540 receives a command packet containing command information to be sent to the coordinator 120 from the CPU 500, Receives the information, and issues a command to the coordinator 120.

The WSN module 540 may issue a detach command and a join command to the coordinator 120 and the detach command is an instruction to detach the sensor node 130 included in the first cluster managed by the first coordinator from the first cluster , The join command is an instruction to join a specific sensor node to the second cluster 140. [

I / F communication is performed between the CPU 500 and the WSN module 540, and the CPU transmits an instruction packet to the WSN module unit through the I / F communication, and the WSN module transfers the data packet to the CPU. More specifically, the command generation unit of the CPU 500 transmits a command packet to the WSN module 540, and the storage unit of the CPU 500 receives the data packet from the WSN module 540 and stores it in the database.

The WSN module 540 instructs the specific coordinator 120 to separate and join the sensor node 130 by using the command packet, which is obtained by processing the cluster information received from each coordinator into a packet form .

6 is a flowchart illustrating a procedure of a connection redistribution method of a wireless sensor network system according to the present invention.

The connection redistribution method of a wireless sensor network system according to the present invention is characterized in that the sink node 110 receives (1) receiving cluster information from a plurality of coordinators 120 (S610), (2) A step S620 of storing the received cluster information, a step S630 of analyzing the stored cluster information, a step of generating a command to be dropped to the coordinator S640 (S650) instructing the first coordinator to separate the specific sensor node, and instructing the second coordinator to merge the separated nodes (S670).

The cluster information includes cluster traffic information, node information in a cluster, and superframe information of a cluster.

Since the sink node 110 receives cluster information from all the coordinators, the sink node 110 also receives the cluster information from the first coordinator and the second coordinator described in FIG. 6 (S610).

The sink node 110 stores the received cluster information in a database.

The sink node 110 generates a schedule so that superframes of the respective clusters are not overlapped temporally from the superframe information of the stored clusters. The sink node 110 informs the coordinator of the schedule so that a beacon is generated according to the generated schedule.

The sink node 110 analyzes the cluster traffic information using the stored database to determine whether the specific cluster is a congested cluster. Whether or not the cluster is congested depends on whether or not the traffic of the cluster exceeds the threshold transmission amount. As a result of the determination, the congested cluster is referred to as the first cluster. A sensor node to be separated from among the sensor nodes included in the first cluster is selected and a second cluster to join the sensor nodes to be separated is selected.

The command frame for separating the selected sensor node in the first cluster includes command type information (leave), time synchronization information, frame length information, destination node address information, source node address information, payload information (coordinator information and sensor node information ), An error check (CRC), and the like.

The command frame to join the selected sensor nodes in the second cluster includes command type information, time synchronization information, frame length information, destination node address information, source node address information, payload information (coordinator information and sensor node information ), An error check (CRC), and the like.

The sink node 110 transmits a separation command S650 to the first coordinator in accordance with the timing of the second contention period of the superframe of the first coordinator. The first coordinator separates the corresponding sensor node, Lt; / RTI > The sink node 110 selects the second coordinator and sends an instruction frame to join the separated sensor node 130. [ At this time, the node access and data transmission request of the sensor node 130 joined to the second coordinator uses the second contention period of the superframe of the second coordinator. The data transmission of the newly joined sensor node 130 is transmitted in the next superframe.

FIG. 7 shows a flowchart of a node redistribution method by traffic analysis according to the present invention.

The cluster information analysis step S630 of FIG. 6 calculates the traffic of the cluster by summing the traffic per unit time for each sensor included in each cluster, and determines the cluster to be redistributed when the traffic of the calculated cluster exceeds the threshold transmission amount . This is referred to as a first cluster.

The program code for calculating traffic per unit time for each sensor node included in each cluster is as follows.

for (i = 0; i < L: i ++)

for (j = 0; j < M [i]: j ++)

traffic_buffer [i] [j] = wsn_buffer [i] [j] / T;

The L denotes the number of clusters, M [i] denotes the number of sensor nodes included in the i-th cluster, wsn_buffer denotes buffer size (traffic) of each sensor node, and traffic_buffer denotes traffic per unit time per sensor node . T represents the unit time.

The program code for summing the traffic per unit time for each sensor node calculated for each cluster is as follows.

for (i = 0; i < L: i ++)

for (j = 0; j < M [i]: j ++)

cluster_buffer [i] + = traffic_buffer [i] [j];

L denotes the number of clusters, M [i] denotes the number of sensor nodes included in the i-th cluster, and T denotes unit time. And the traffic per unit time per sensor (traffic_buffer [i] [j]) is added to the per-cluster traffic (cluster_buffer [i]).

The pseudo code for confirming whether or not the per-cluster traffic exceeds the threshold transmission amount is as follows.

for (i = 0; i < L: i ++)

if (? <cluster_buffer [i])

Exceeding the threshold transmission volume

And γ represents the threshold transmission amount. The critical transmission amount (γ) is calculated experimentally considering the traffic processing limit of the sink node of the wireless sensor network, the traffic of the entire cluster, the structure of the cluster, and the like.

When the traffic (cluster_buffer [i]) of a specific cluster exceeds the threshold transmission amount (gamma), the cluster is referred to as the first cluster as described above. A sensor node to be separated in the first cluster is selected. For example, the sensor node having the largest transmission amount is selected by the sensor node to be separated and separated from the first cluster so that the traffic of the first cluster is less than the critical transmission amount. When the traffic of the first cluster greatly exceeds the threshold transmission amount, it is possible to separate two or more sensor nodes.

The threshold transmission amount should be set to be larger than the cluster average traffic. For example, the threshold transmission amount can be set to 140% of the average traffic of the cluster. Cluster mean traffic is the sum of the traffic per unit time of all the sensor nodes included in the wireless sensor network connected to the sink node divided by the number of clusters. If the threshold transmission rate is set smaller than the average traffic of the cluster, there is a problem that the traffic of each cluster can not be all below the critical transmission rate by redistributing the sensor node. The present invention is intended to increase the transmission efficiency and ensure the timeliness by redistributing the nodes included in the clusters so that the traffic of all the clusters is less than the critical transmission amount, and if the transmission amount is excessively large as a whole, the benefit of applying the present invention will be small.

However, in the case where the overall amount of traffic is excessive, a method of redistributing nodes so that the traffic of each cluster is equal can be used. At this time, the node having the smallest traffic per unit time among the nodes that make the traffic of the cluster less than the threshold transmission amount is divided into clusters. However, in this case, it would be desirable to modify the entire structure of the wireless sensor network to improve the system acceptable traffic.

For example, if the threshold transmission amount is set to 70% of the total available capacity, the throughput of data transmission can be improved by redistributing the nodes of the cluster.

Meanwhile, the sensor node can request the coordinator node to transmit the beacon signal of the superframe received by itself to the sensor node. Specifically, the sink node 110 requests only the first coordinator 120 to separate a specific sensor node, and the sink node 110 does not request the second coordinator 120 to join the specific sensor node, The sensor node 130 separated from the first coordinator may request the second coordinator 120 to join. The separated sensor node 130 makes a request for joining by using the second frame of the superframe of the coordinator node that transmits the received beacon signal to itself.

While the present invention has been described in detail with reference to the accompanying drawings, it is to be understood that the invention is not limited to the above-described embodiments. Those skilled in the art will appreciate that various modifications, Of course, this is possible. Accordingly, the scope of protection of the present invention should not be limited to the above-described embodiments, but should be determined by the description of the following claims.

110: sink node
120: coordinator node
130: sensor node
140: Cluster
500: CPU
540: WSN module

Claims (12)

1. A wireless sensor network system comprising a plurality of clusters each including a coordinator node and at least one sensor node,
i) analyzing the amount of traffic in each of the clusters and transmitting a separation or merging command of a sensor node to a coordinator node selected from among the coordinator nodes based on the analysis result, ii) A sink node that receives a cluster-specific superframe containing a data transmission schedule for all nodes in the cluster from a plurality of coordinator nodes included in a plurality of clusters and creates a data transmission schedule so that a plurality of received superframes are not overlapped, In addition,
The superframe of the sink node includes an active period and an inactive period, which are configured by a beacon, a first contention period, a second contention period, and an allocation period,
The coordinator node, which has received the separation or merging command of the sensor node, separates or joins the sensor node from the cluster according to the separation or join command of the received sink node,
Wherein a sensor node to be separated from the cluster and to be joined to another cluster requests a GTS allocation for data transmission using a second contention period of a superframe of another cluster.
2. The method of claim 1, wherein the sink node
In order to analyze the amount of traffic in each cluster, the traffic of the cluster is calculated by summing traffic per unit time per each sensor node, and when the traffic of the cluster exceeds the threshold transmission amount, Generating the detach command to detach the node, and generating the join command to join the detached sensor node to another cluster. &Lt; Desc / Clms Page number 19 &gt;
delete delete delete 1. A wireless sensor network system comprising a plurality of clusters each including a coordinator node and at least one sensor node,
i) analyzing a traffic volume in each of the clusters and transmitting a separation command of a sensor node to a selected one of the coordinator nodes based on an analysis result; and ii) A sink node that receives a cluster-specific superframe containing a data transmission schedule for all nodes from a plurality of coordinator nodes included in a plurality of clusters and creates a data transmission schedule so that a plurality of received superframes do not overlap, Including,
The superframe includes a beacon, a first contention period, a second contention period, an activation period and an inactivation period,
The coordinator node receiving the sensor node separation command separates the sensor node from the cluster according to the separation command,
Wherein the sensor node separated from the cluster requests a GTS allocation for data transmission using a second contention period of a superframe of another cluster.
The method according to claim 6,
The sensor node, which is separated according to the sink node's separation command, makes a joining request to the coordinator node,
Wherein the coordinator node receiving the joining request from the sensor node, in response to the joining request, joins the sensor node to the cluster and then assigns the GTS of its own superframe. Network system.
1. A connection redistribution method for a wireless sensor network system comprising a plurality of clusters each including a coordinator node and at least one sensor node, and a sink node for collecting cluster information from the plurality of clusters,
The sink node
(1) receiving cluster information from the plurality of coordinator nodes and storing the cluster information in a database;
(2) generating a schedule such that superframes of the clusters are not overlapped temporally from the received cluster information;
(3) analyzing traffic of the stored cluster information;
(4) generating a sensor detachment or confluence command in the coordinator, the method comprising: instructing the first coordinator to detach the sensor node in the first cluster; and instructing the second coordinator to join the sensor node to the second cluster Comprising the steps of:
Wherein the superframe includes an active period and an inactive period, the active period including a beacon, a first contention period, a second contention period, and an allocation period, wherein the first contention period is used for requesting connection and data transmission by the sensor node, Wherein the second contention period is used by the separated sensor node to request cluster access and data transmission, and the allocation period is used to transmit actual data.
The method of claim 8, wherein
Wherein analyzing the traffic of the cluster information comprises calculating traffic of the cluster by summing traffic per unit time of each node per cluster and determining whether the traffic of the calculated cluster exceeds the critical transmission amount
A method for access redistribution in a wireless sensor network system.
The method of claim 8, wherein
Wherein in the step of generating the command, the separation command selects a sensor node having the largest transmission amount in a cluster from a sensor node to be separated in the first cluster, And a cluster is selected.
A method for access redistribution in a wireless sensor network system.
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