KR20100093216A - Sensor node and method for controlling backoff range of wireless sensor network - Google Patents

Abstract

PURPOSE: A sensor node for controlling back-off range of a wireless sensor network and a method thereof are provided to ensure differentiated packet transmission depending on the quality of sensing data by reflecting the important degree of the sensing data to a priority of a packet. CONSTITUTION: A priority setting unit(203) determines the priority of a generated packet of a packet generating unit(202), and stores the priority at a preamble for the synchronization of a sensor node. A back-off range setting unit(205) sets up the back-off range of a transmission range based on at least one priority of the priority of the packet, the priority of a packet transmitted from another sensor node, and the priority of a packet received through overhearing.

Description

Sensor node and method for controlling backoff range of wireless sensor network

Wireless sensor network technology. In particular, the present invention relates to a technique for guaranteeing QoS through back-off range adjustment in a wireless sensor network system.

Recently, sensor nodes (or motes) in which various sensors and small processors are combined form an autonomous network, and wireless sensor networks have been actively developed to monitor environment, ecology, security, and mobility of a specific area.

In these wireless sensor networks, a plurality of sensor nodes sense and process the surrounding environment information and then transmit the desired information to the sink node that can communicate with the user. This information can be used in a variety of applications, including environmental monitoring, detection of emergency situations such as natural disasters, and tracking the movement of objects.

In particular, in applications such as the detection of a disaster situation, the information (or event) needs to be delivered quickly and reliably. To this end, differentiated processing technology is required according to the importance of data, but most sensor networks are currently processing and transmitting data uniformly regardless of the information.

The reason why such a differentiation technology is difficult to implement in a wireless sensor network is that it is difficult to guarantee stable transmission due to frequent quality changes of wireless media and frequent collisions between sensor nodes.

In the process of transmitting data from the sensor node that generated the data to the destination sensor node, the data processing time, transmission queue waiting time, backoff delay time for the use of the wireless channel, transmission in each sensor node In general, a propagation delay occurs due to retransmission time due to a failure.

For example, due to the characteristics of the wireless sensor network, since a plurality of sensor nodes transmit data to one or a few sink sensor nodes, packet reception is concentrated in an area where a relatively large number of sensor nodes or data are generated close to the sink sensor node, This naturally leads to network congestion. In this local congestion situation, transmission delay time is further increased due to transmission failure due to queue waiting for transmission in a sensor node, contention for channel use among sensor nodes to transmit a packet, and hidden node problem.

Due to the environmental and technical characteristics of the wireless sensor network, there is a difficulty in providing QoS (Quality of Service) or efficient packet transmission. Nevertheless, in recent years, the application fields of the wireless sensor network are becoming more diverse, and there is a need to provide QoS according to data characteristics.

In the present specification, a wireless sensor network technology capable of determining the priority of a packet according to the importance of sensed information and adaptively adjusting the back-off range in consideration of the priority of the packet and the surrounding network situation provides a QoS. Is initiated.

More specifically, the sensor node of the wireless sensor network according to an aspect of the present invention, the packet generation unit for generating a packet for the sensing data; A priority setting unit which determines a priority of packets according to the importance of sensing data, and stores the priority in a preamble for synchronization with other sensor nodes; And a back off range of the transport packet using at least one priority among generated priority of the generated packet, priority of a packet received from another sensor node, and priority of a packet received through overhearing from another sensor node. A back off range setting unit for setting a; It may include.

In addition, the method of adjusting a back off range of a wireless sensor network according to an aspect of the present invention includes generating a packet for sensing data; Determining priorities of packets according to importance of sensing data, and storing the priorities in a preamble for synchronization with other sensor nodes; And a back off range of the transport packet using at least one priority among generated priority of the generated packet, priority of a packet received from another sensor node, and priority of a packet received through overhearing from another sensor node. Setting up; It may include.

In addition, according to an aspect of the present invention, the preamble may include both information about the priority of the packet to be transmitted currently and the priority of the packet to be transmitted next.

Further, according to an aspect of the present invention, the back off range compares the priority of the packet generated by itself or the priority of the packet received from another sensor node with the priority of the packet received through eavesdropping from another sensor node. It is possible to determine relative priorities, and to be adaptively adjusted according to these relative priorities.

According to the disclosed contents, since the back off range is determined according to the priority of the packet, and the priority of the packet reflects the importance of the sensing data, it is possible to guarantee differentiated packet transmission according to the quality of the sensing data. Also, in determining the back off range, the back off range is determined based on the priority of packets owned by neighboring sensor nodes as well as the priority of the packets owned by the neighbor. It is possible to determine the off range.

Hereinafter, specific examples for carrying out the present invention will be described in detail with reference to the accompanying drawings. The embodiments described below are intended to illustrate the present invention by way of example and the scope of the present invention is not limited to the specific embodiments.

1 illustrates a wireless sensor network system in accordance with an embodiment of the present invention.

Referring to FIG. 1, the wireless sensor network system 100 may include a plurality of sensor nodes 101 installed in a predetermined area.

Each sensor node (eg, 101-1) uses a sensor module to acquire surrounding information (eg, information on environment, ecology, security, movement state, etc.), and transmits the acquired information using a communication module. It is possible.

Sensor nodes 101 form a wireless network. That is, the sensor nodes 101 may share a radio channel with each other and transmit and receive packets regarding information sensed through the radio channel. As a wireless protocol for communication, the B-MAC protocol may be used, and the sensor nodes 101 may transmit and receive a preamble signal to synchronize with each other before the communication starts.

For example, when sensor node A 101-1 acquires ambient temperature information and transmits it to sensor node B 101-2, sensor node B 101-2 acquires ambient temperature information and sensor node A acquired by itself. It is possible to collect the temperature information received from the 101-1 and transmit it to the sink node 101-3 which is communicably connected to the user 102.

Therefore, the wireless sensor network system 100 according to the present embodiment is formed in a fire-prone area, and the user 102 uses the information acquired by the sensor nodes 101 to determine whether or not a temperature situation or fire occurs in the area. It is possible to monitor.

In order for the user 102 to accurately monitor the situation in a specific region, a quality of service (QoS) must be guaranteed for information transfer between the sensor nodes 101. When the sensor nodes 101 according to the present embodiment transmit and receive information, QoS can be guaranteed by adaptively adjusting the backoff range of the packet in consideration of the importance of the information and the network situation. Do.

2 illustrates a sensor node according to an embodiment of the present invention.

Referring to FIG. 2, the sensor node 200 includes a sensor unit 201, a packet generator 202, a priority setting unit 203, a synchronization unit 204, a back off range setting unit 205, and packet transmission / reception. It may include a portion 206.

The sensor unit 201 generates sensing data by monitoring the surrounding environment. For example, the sensor unit 201 may periodically generate ambient temperature to generate digital data about temperature for each time.

The packet generator 202 generates a packet for sensing data. Here, the packet refers to a transmission form of sensing data for communication with other sensor nodes. For example, the packet generator 202 may generate a packet for sensing data based on the TOS_Msg format provided by Tiny OS 1.x for communication between sensor nodes.

The priority setting unit 203 determines the priority of the packet according to the importance of the sensing data.

Since the sensing data is delivered in the form of a packet, the priority of the packet may be the priority of the sensing data. Therefore, the priority of the packet classifies the sensing data according to importance, gives a differential priority to each of the classified sensing data, and when packetizing the sensing data, information about the priority is assigned to a specific field on the packet format. It can be determined by the method of generating a packet. At this time, the priority of the sensing data and the priority according to the importance may be variously defined by the user according to application characteristics.

In addition, the priority setting unit 203 adds the priority of the packet to the preamble for synchronization with other sensor nodes. That is, the part where the priority information is stored may be a preamble area on the packet format.

Here, the preamble area refers to an area corresponding to a preamble signal transmitted and received before packet transmission for synchronization with other sensor nodes. For example, when the sensor node uses a B-MAC-based communication protocol, it is possible to determine the priority of the packet by adding a priority to the TOS_Msg format preamble provided by Tiny OS 1.x.

In addition, when the priority setting unit 203 adds the priority of the packet to the preamble, it is possible to add the priority of the current packet and the priority of the next packet to be transmitted. Accordingly, the sensor node 200 receiving the preamble signal can overhear the priority of packets transmitted by the neighbor sensor nodes.

The synchronizer 204 transmits and receives the preamble signal with the peripheral sensor nodes.

The back off range setting unit 205 sets the back off range of the transport packet by using the priority of the packet.

The transport packet may be a packet generated or received from another sensor node and to be transmitted to another sensor node. For example, the transport packet may be its own packet generated by the packet generator 202 or a packet received from another sensor node through the packet transceiver 206.

The backoff range may be a range of waiting time for transmitting a packet. That is, it is possible for any packet transmission latency to be selected at random within a given back off range. For example, if the back off range has a large value, the transmission wait time may be probabilistically long, and if the back off range has a small value, the transmission wait time may be shortened probabilisticly.

The priority of the packet considered to set the back off range is the priority of the packet generated by the packet generator 202, the priority of the packet received from the packet transceiver 206, and the received signal from the synchronizer 204. This may be the priority of packets of neighboring nodes specified in the preamble.

For a more detailed description, the back off range setting method is divided into a static setting mode and a dynamic setting mode as follows.

Static configuration mode is a method of determining the back off range by considering only the priority of the packet to be transmitted. For example, when determining the back off range between the packets generated by the packet generator 202, the higher the priority of each packet may be a method of giving a back off range of a smaller value. As another example, when a packet generated by the packet generator 202 and a packet received through the packet transceiver 206 contend, it is possible to set a back off range determined according to the priority of each packet.

The dynamic configuration mode refers to a method of determining the back off range by considering not only the priority of the packet to be transmitted but also the priority of the packet to be transmitted by other sensor nodes in the vicinity. As described above, the sensor node 200 according to the present embodiment transmits and receives a preamble signal before packet transmission, and the preamble signal includes priority information of the packet to be transmitted now and next, and thus received through the synchronization unit 204. It is possible to grasp the situation of the peripheral sensor node from the preamble signal. For example, in the dynamic configuration mode, the priority of the packet generated by the packet generator 202 and the peripheral sensor node received by the synchronizer 204 are compared with the priority of the next packet to determine the relative priority. It is possible to determine the back off range according to the relative priority.

Therefore, when the sensor node transmits the packet, the backoff range is adaptively set in consideration of both the packet priority and the surrounding network situation, thereby improving the overall wireless channel usage efficiency of the network.

3 illustrates a packet format according to an embodiment of the present invention.

Referring to FIG. 3, it can be seen that new fields are added in the TOS_Msg format provided by TinyOS 1.x.

Looking at the added fields, the priority field 301 indicates the priority of the packet and is designated in the preamble area on the packet format. The priority field 301 may be designated as 1 byte, and the priority of the next packet to be transmitted may be specified in the upper 4 bits and the priority of the current packet in the lower 4 bits.

The pinversion field 302 is used to improve the data processing delay for high priority packets that may occur during TinyOS-based transmit / receive processing, and the pseqnum field 303 is used to evaluate packet loss rate by priority. The sendTime field 304 is used to evaluate the delivery time of the packet.

4 illustrates a static back off range in accordance with an embodiment of the present invention.

In FIG. 4, the static back off range may be used when the back off range setting unit 205 considers only the priority of the packet to be transmitted when setting the back off range of the packet. In this case, the packet to be transmitted by itself may be a packet received from the packet generator 202 or a packet received from another sensor node through the packet transceiver 206.

For example, the back off range setting unit 205 may apply a back off range of a smaller range as the priority of the packet to be transmitted before the packet transmission increases. In addition, since the waiting time is relatively shorter as the back off range is smaller, it is possible for the packet transceiver 206 to guarantee the radio channel occupancy rate of a packet having a high priority when transmitting the packet.

5 illustrates a dynamic back off range according to one embodiment of the invention.

In FIG. 5, when the back off range setting unit 205 sets the back off range of a packet, the dynamic back off range considers both the priority of the packet to be transmitted and the priority of the packet to be transmitted by another node. Can be used.

For example, the back off range setting unit 205 compares the priority of the packet to be transmitted before the packet transmission with the priority of the packet to be transmitted by another sensor node received through eavesdropping, which is a relative priority of the packet to be transmitted. It is possible to determine the order. And it is possible to apply a differential back off range based on this order.

As an example, each back off range according to the order may be expressed as follows.

Order 0 = Range

Order N = Range × N + Order 0's Max Value (N = 1,2,3,4)

In other words, according to the relative order of comparison, Order 0 has a random value within a short range to set the back-off time.From Order N, the range increases according to the order of the order, and the random value is increased within the increased range. After setting, it is possible to set the back off time by adding the maximum value that can be set to Order 0.

6 illustrates an operation of a sensor node according to an embodiment of the present invention.

In Fig. 6, A, B, C, and D represent sensor nodes, respectively, and P1, P2, and P3 represent packets.

The sensor nodes A, B, C, and D (601, 602, 603, 604) can transmit and receive a preamble signal before packet transmission, respectively, to synchronize. When generating a packet for sensing data, it is possible to generate a packet by adding a priority to the preamble according to the importance of the sensing data. In addition, the preamble may include both priority information of a packet currently to be transmitted and priority information of a packet to be transmitted next. Further, when setting the back off range of the packet, it is possible to adaptively set the back off range in consideration of the priority of the packet to be transmitted by itself and / or the priority of the packet to be transmitted by the neighboring sensor nodes.

As an example, the A sensor node 601 will be described.

The A sensor node 601 attempts to transmit the current P1 packet, and then attempts to transmit the P2 packet. At this time, each P1 packet and P2 packet have a transmission waiting time, which can be arbitrarily determined within a set back off range. In addition, the back off ranges of each P1 packet and P2 packet are given differentially according to the importance of sensing data. For example, if the importance of the sensing data with respect to the P1 packet is higher than the importance of the sensing data with respect to the P2 packet, it is possible to give the P1 packet a higher priority and a shorter back off range.

In addition, the A sensor node 601 may transmit the priority information of the P1 packet and the priority information of the P2 packet to a neighboring sensor node (eg, 602) in a preamble signal before transmitting the P1 packet. For example, the B sensor node 602 that has received the P1 packet can listen in advance to the priority information of the P2 packet, which is the packet that the A sensor node 601 will transmit next.

As another example, the B sensor node 602 will be described.

The B sensor node 602 intends to transmit the P1 packet received from the A sensor node 601 to the C sensor node 603. At this time, when the B sensor node 602 determines the back off range of the P1 packet, not only the priority of the P1 packet but also the priority of the P3 packet that the D sensor node 604 intends to transmit and the A sensor node 601 intends to transmit. It is also possible to consider the priority of P2 packets. The P3 packet is a packet that the D sensor node 604 intends to transmit next, and the information about the priority of the P3 packet may be detected by the B sensor node 602 by receiving the preamble signal from the D sensor node 604. . Information regarding the priority of the P2 packet may also be obtained by the B sensor node 602 receiving the preamble signal from the A sensor node 601.

In the B sensor node 602, to determine the back off range of the P1 packet, the B sensor node 602 first determines the priority of the P1 packet, and the priority of the P2 packet to be transmitted by the A sensor node 601, which is a neighbor node. Then, another neighbor node D sensor node 604 compares the priorities of the P3 packets to be transmitted to each other and calculates a relative priority order. The backoff range is given according to the calculated order. Therefore, even if the priority of the P1 packet is very low and the back off range is set large, if there are no packets to be transmitted by neighboring sensor nodes, the relative priority order is preceded (has a small value). It is possible for the range to be adaptively adjusted. This method allows relative channel occupancy ordering according to the priority comparison of packets with each other in a situation where channel conflict between A (601), B (602), and D (604) sharing a radio channel is inevitable.

7 illustrates a method of setting a back off range of a wireless sensor network according to an embodiment of the present invention. Referring to FIG. 7, the method for setting the back off range according to the present embodiment is as follows.

First, a packet for sensing data is generated (701). For example, the packet generation unit 202 may receive sensing data from the sensor unit 201 and generate a packet based on the TOS_Msg format provided by TinyOS 1.x for the received sensing data.

The priority of the packet is then determined (702). For example, the priority setting unit 203 classifies the sensing data of the sensor unit 201 according to importance, assigns the differential priority to each of the classified sensing data, and then assigns the priority to the corresponding sensing data. It is possible to add to the preamble area of the packet for.

Subsequently, the preamble signal is transmitted to surrounding sensor nodes (703). In this case, as described above, the preamble signal may include both priority information of a packet to be transmitted currently and priority information of a packet to be transmitted next.

In operation 704, it is determined whether a preamble signal is received from a peripheral sensor node.

If it is determined that the preamble signal is not received, the back off range is set according to the static setting mode (705). For example, it is possible to give the packet a back off range determined based on the priority of the packet to be transmitted by itself, such as a packet generated by itself or received from another sensor node. In this case, the higher the priority, the smaller the back off range can be set.

As a result of the determination, when the neighbor sensor node receives the packet priority information to be transmitted through the reception of the preamble signal, the back off range is set according to the dynamic configuration mode (706). For example, the back-off range is determined by considering the priority of packets to be transmitted by the preamble signal, such as packets generated by themselves or received from other sensor nodes, and the priority of packets to be transmitted by neighboring sensor nodes. It is possible to do In this case, it is possible to determine the relative priority by comparing the priority of the packet to be transmitted with the priority of the packet to be transmitted by the peripheral sensor node, and to set the differential back-off range according to the relative priority.

As described in detail above, according to the disclosed contents, it can be seen that the back off range can be adaptively adjusted according to the priority of packets and / or network conditions of the surroundings. Therefore, it is possible to guarantee the preemption of radio channel of high priority packet, and it is possible to increase the probability of preemption of wireless channel according to the situation of the surrounding network even for the packet of low priority, thereby guaranteeing the overall efficiency of use of the radio channel and QoS. You can do it.

1 illustrates a wireless sensor network system in accordance with an embodiment of the present invention.

2 shows a configuration of a sensor node according to an embodiment of the present invention.

3 illustrates a packet format according to an embodiment of the present invention.

4 illustrates a static back off range in accordance with an embodiment of the present invention.

5 illustrates a dynamic back off range according to one embodiment of the invention.

6 is a flowchart illustrating an operation of a sensor node according to an embodiment of the present invention.

7 illustrates a method of setting a back off range of a wireless sensor network according to an embodiment of the present invention.

Claims (6)

A packet generator for generating a packet for sensing data; A priority setting unit determining a priority of the packet according to the importance of the sensing data and storing the priority in a preamble for synchronization with other sensor nodes; And Backoff of the transport packet using at least one priority of the generated packet, the priority of the packet received from the other sensor node, and the priority of the packet received through overhearing from the other sensor node. A back off range setting unit for setting a range; Sensor node of the wireless sensor network comprising a. The method of claim 1, Wherein the preamble includes information regarding a priority of a packet to be transmitted currently and a priority of a packet to be transmitted next. The method of claim 1, The back off range setting unit determines a relative priority by comparing the priority of the generated packet or the priority of the packet received from the other sensor node with the priority of the packet received through the other sensor node. The sensor node of the wireless sensor network, characterized in that for setting the back off range according to the relative priority. Generating a packet for sensing data; Determining a priority of the packet according to the importance of the sensing data and storing the priority in a preamble for synchronization with other sensor nodes; And Backoff of the transport packet using at least one priority of the generated packet, the priority of the packet received from the other sensor node, and the priority of the packet received through overhearing from the other sensor node. Setting a range; Method for setting a back off range of a wireless sensor network comprising a. The method of claim 4, wherein The preamble includes information on the priority of the packet to be transmitted currently and the priority of the packet to be transmitted next. The method of claim 4, wherein The setting of the back off range may be performed by comparing the priority of the generated packet or the priority of the packet received from the other sensor node with the priority of the packet received through the other sensor node. Determining a rank and setting the back off range according to the relative priority.

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