KR101174125B1 - MAC Protocol based on Priority and method for data transmission in Sensor Network - Google Patents

Abstract

The present invention randomly executes only once upon initial startup of all nodes participating in the sensor network, giving priority to the nodes while allowing each node to share node information to neighboring nodes two hops apart. Forming a random access interval I; A slot reservation period for allocating a reservation slot from the node having the highest priority according to the priority given in the random access period (I) and transmitting the reservation message to reserve the transmission slot according to the presence or absence of data to be transmitted. Forming (II); And forming a data transmission section III for transmitting data to the neighboring node through a transmission slot reserved by the reservation message. And assigns a priority of the nodes participating in the sensor network, and allocates a reservation slot from the node having the highest priority according to the priority, and reserves a transmission slot necessary for data transmission through the assigned reservation slot. And transmit / receive data with a neighbor node that is activated through a transmission slot reserved by the reservation message.

Sensor Network, Priority, Mac Protocol, Slot Reservation

Description

Priority-based MAC protocol formation method and data transmission method in the sensor network using the same {MAC Protocol based on Priority and method for data transmission in Sensor Network}

The present invention relates to a sensor network, and in particular, a method for forming a priority-based MAC protocol for preventing collision between nodes and minimizing energy loss of nodes through slot reservation intervals determined by a non-competitive method, and the MAC The present invention relates to a data transmission method in a sensor network to which a protocol is applied.

The present specification describes a sensor network in an underwater environment in which a plurality of nodes are distributed and installed in the water.

First, the sensor network technology attaches a sensor or an electronic tag to a necessary object or place, detects recognition information, surrounding environment information, and location information of the object and connects it to the network in real time to implement a communication environment. . In particular, the sensor network is mainly used for the purpose of monitoring the environment, and it distributes the sensors in a dangerous environment and collects and transmits various information about them.

The sensor network technology is also applied to the marine environment. This is due to the increasing demand for marine water resources and the environment, the development of sea resources due to land resource limitations, the increasing social demands due to the interest of alternative resources, and the need to measure water quality. 'S underwater sensor network is getting attention. The underwater sensor network has been applied to marine ecosystem survey, seabed resource exploration, pollutant and pollutant measurement, weather observation and tsunami warning, and its field of use is gradually expanding.

Unlike the terrestrial sensor network, the underwater sensor network has characteristics such as limited radio bandwidth, high energy cost, long propagation delay, and low sound wave speed of the wireless transmission medium. This characteristic causes a decrease in the accuracy of information transmission and the inability to maintain a stable communication service.

Above all, the underwater sensor network has a problem in that data transmission is not normally performed because channel collision occurs because each node shares a wireless transmission medium for transmitting data from the node.

Therefore, a communication method that actively responds to the conditions of the underwater environment was needed, and a MAC (Middle Access Control) protocol suitable for the underwater sensor network has been proposed.

An example is 'Method of Access Control Protocol for Underwater Acoustic Sensor Network (Author Jang Gil-woong)' (hereinafter referred to as 'priority literature') of the Korean Institute of Information Scientists and Engineers Vol.

The protocol structure of this prior document is shown in FIG. Referring to FIG. 1, there is one transmission cycle period, and the transmission cycle period is again a slot reservation period (ii) and a data transmission period having a slot time for data transmission. data transmission period).

Accordingly, since the node can reserve a slot for data transmission by the slot reservation section (ii), it is possible to reduce the occurrence of channel collision during data transmission of the nodes. In addition, the data transmission interval is also divided into a plurality of slots to be transmitted to try to solve the problem of collision during data transmission.

However, the above-mentioned prior art has the following problems.

First, although the slot reservation section (ii) exists in the MAC protocol structure, slot reservation through the slot reservation section (ii) reserves a slot according to a competition scheme. This causes a problem that two or more nodes reserve the same slot. This leads to collisions when nodes transmit and receive data.

In addition, even when a reservation message is transmitted to reserve the slot, there is a possibility of collision because it is a competition method. This problem occurs because the nodes participating in the underwater sensor network do not correctly share the information of neighboring nodes.

In addition, all nodes participating in the underwater sensor network remain active in the slot reservation section (ii). This leads to energy loss of the nodes. That is, all nodes constituting the underwater sensor network should perform a function of collecting and transmitting information for as long as possible with a constant battery power. However, since all nodes remain active in the slot reservation section ii, the slot reservation section ii becomes longer by that amount, which causes energy loss. This problem results in a problem that prevents the smooth collection of information in the underwater environment.

Accordingly, an object of the present invention is to solve the above problem, and the nodes participating in the sensor network share information up to neighboring two hop nodes.

Another object of the present invention is to give priority to all nodes participating in the sensor network, and to allocate slots necessary for transmitting data in order according to the priority.

Another object of the present invention is to minimize energy loss in the slot reservation interval according to priority allocation due to information sharing between nodes.

According to a feature of the present invention for achieving the above object, prior to the initial start-up of all nodes participating in the sensor network, each node shares the priority of the predetermined unique information of each node up to neighboring nodes two hops (hop) Forming a random access interval (I) for assigning a priority to the reserved slot allocation to the node by scheduling; A slot reservation period for allocating a reservation slot from the node having the highest priority according to the priority given in the random access period (I) and transmitting the reservation message to reserve the transmission slot according to the presence or absence of data to be transmitted. Forming (II); And forming a data transmission section (III) for transmitting data to the neighboring node through a transmission slot reserved by the reservation message. If the priority is not given to some nodes in the random access interval (I), the priority-based MAC protocol forming method for repeating the priority scheduling to be given to all nodes is provided. do.

The priority scheduling assigns a priority based on at least one of a unique ID of the node, a channel state of the node, a power state of the node, and a remaining power amount of the node.

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The data transmission section III is an entire sleep mode section, and only nodes for data transmission / reception are active in transmission slots reserved through the reservation message.

According to another feature of the invention, the first step of giving priority to the nodes participating in the sensor network by the above-described MAC protocol forming method; A second step of allocating a reservation slot from the node having the highest priority according to the priority, and transmitting a reservation message to reserve a transmission slot necessary for data transmission through the allocated reservation slot; And a third step of performing data transmission / reception with the neighbor node through a transmission slot reserved by the reservation message.

In the first step, in the initial operation of the node, according to the random access execution of the MAC protocol, each node shares the node information to neighbor nodes two hops away from itself. step; And determining the priorities of the nodes using the shared node information.

The second step transmits the reservation message only when there is data to be transmitted among the nodes.

When the reservation message is transmitted, a neighboring node adjacent to the node that has transmitted the reservation message reserves only transmission slots other than the transmission slots reserved by the reservation message by the priority.

In the present invention, all nodes participating in the sensor network exchange information with neighboring nodes and then determine the priority of the nodes, and allocate the reserved slots according to the determined priorities. That is, reserved slots are allocated to each node by priority according to the non-competitive method. Therefore, there is an effect that collision between nodes in the slot reservation section is prevented. In addition, the slot reservation section is shorter than the conventional, it is possible to reduce the energy loss.

When a reserved slot is assigned, when a reserved message is transmitted through the reserved slot to reserve a transmission slot in which data transmission is actually performed, only the corresponding node (i.e., a transmitting node and a receiving node) is activated in a sleep state to transmit and receive data. In this way, battery power consumption of the nodes is minimized.

Hereinafter, a priority-based MAC protocol and a data transmission method in a sensor network to which the present invention is applied will be described in detail with reference to a preferred embodiment shown in the accompanying drawings.

In the embodiment of the present invention, it is assumed that the time synchronization of each node is previously set in advance, and the ID of each node is differently assigned. In the description, the term 'node' refers to an object capable of transmitting collected information to another node or receiving information from another node. That is, there is no control node for controlling the nodes, and each node communicates with other nodes directly or through other nodes by utilizing the information that it can have.

2 is a structural diagram of a priority-based MAC protocol according to an embodiment of the present invention.

2, the MAC protocol includes a random access period (I) for assigning priorities, a slot reservation period (II) for reserving transmission slots for data transmission, and a reservation. It is divided into a data transmission period (III) for transmitting data through the transmission slot. The sections II and III may be referred to as a transmission cycle period (IV). Look at each section in detail.

The random access section I is executed only once at the time of initial activation of all nodes participating in the sensor network, and each node exchanges its own information with a neighboring node and shares them with each other. It is also a section for determining the priority of nodes using information shared with each other. Of course, if the random access section (I) does not give priority to all nodes by executing only once, it may be repeated to give priority to all nodes. When the repetition is performed, the node is performed only for the remaining nodes except for nodes that have already been given priority.

The priority is determined by priority scheduling. Priority scheduling is as follows.

"Priority_Selection Func (node ID, RSSI, Power status)" --- Equation (1).

Here, 'node ID' is a unique value of the node, 'RSSI (Received Signal Strength Intensity)' refers to the channel status of the node, and 'Power status' refers to the power status of the node.

The slot reservation section (II) allocates a reservation slot in a non-competitive manner from the node having the highest priority according to the priority of the node given in the random access section (I), and allocates actual data through the reservation slot. This is a section to reserve the transmission slot to transmit. The reservation of the transmission slot is made by sending a reservation message through the reservation slot. That is, the reservation slot performs a function of transmitting the reservation message in the order of priority assignment. Therefore, the reservation message is transmitted only when the node has data to be transmitted by the node. If there is no data to be transmitted, the reservation message is not transmitted. Since the reservation message is a message for reserving a transmission slot by a reservation slot allocated by the priority, only the information for reserving a transmission slot needs to be included.

The data transmission section III is a section in which a node transmitting data and a node receiving the data in a transmission slot reserved through the reservation message in the slot reservation section II are activated in a sleep state and transmit and receive data. That is, the data transmission section III is a sleep mode section in which all nodes are inactive, and only the corresponding nodes are activated according to the reservation message.

Next, a method of transmitting data between nodes in an underwater sensor network by applying the priority-based MAC protocol forming method will be described.

FIG. 3 is a block diagram of a proposed underwater sensor network for explaining an embodiment of the present invention, and FIG. 4 is a block diagram of a state in which a priority is given to a node participating in the underwater sensor network of FIG. 3. 5 is a flowchart illustrating a data transmission method in a sensor network to which a priority-based MAC protocol is applied according to an exemplary embodiment of the present invention.

Here, it is assumed that the transmission ranges of 'node A' to 'node G' participating in the underwater sensor network of FIGS. 3 and 4 are the same, and nodes located within one transmission range can transmit data to each other. .

First, power is applied to all nodes A to G in the underwater sensor network as shown in FIG. 3 to start operation. At this time, the numbers 1 to 7 assigned to the nodes A to G indicate the node ID.

Then, 'Node A' to 'Node G' share their information by randomly exchanging their information with neighboring nodes after a random back off time (s102). The information exchange is performed through the random access interval (I) of the Mac protocol. The random access section I is executed only once the first time after power is applied to the node. Specifically, in accordance with the information exchange of 'Node A' to 'Node G', each node first exchanges information with neighboring nodes one hop apart, and repeats this process, Share information too. That is, in the example of the information exchange, 'node A' exchanges information with 'node B', 'node C', 'node F', and 'node A' means' node B ',' C ',' F 'information, whereas' Node B', 'C', 'F' will have the information of 'Node A'. 'Node B', 'C' and 'F' exchange information with neighbor nodes 'Node D', 'E' and 'G'. When such information exchange between neighboring nodes that are separated by one hop is repeatedly performed, finally, only 'Node A' and 'Node D' are considered, and 'Node A' and 'Node D' are connected to each other via 'Node B'. Since information is exchanged, 'node A' has information of 'node B' and 'node D', and 'node D' has information of 'node B' and 'node A'. In this case, the information exchanged between the nodes is unique information of each node, which is preset, includes a unique ID, a channel state (RSSI), a power state, and the like of the node itself. Therefore, each of the 'node A' to 'node G' can know all the information of the neighbor node within two hops based on itself.

Next, the priority of the 'node A' to 'node G' is determined using the inter-node information (s104). The priority is determined using one or more of the node's unique ID order, channel state, power state. In addition, other information may be used to set priorities. For example, when a node G having a relatively low priority transmits an important or urgent message to other nodes, the priority may be changed to have the highest priority. In this case, the conditions that can be determined as the highest priority are stored in the memory of the nodes A through G, and if the conditions occur, the priority of the nodes is determined again.

An example in which priority is given to 'Node A' to 'Node G' according to the priority assignment process of the random access section I is shown in FIG. 4. 1 to 7 in FIG. 4 indicate priority of nodes. Accordingly, it can be seen that the priority of each node becomes as 'node A'-'node B'-'node F'-'node C'-'node E'-'node D'-'node G'.

As shown in FIG. 4, when the priorities for 'Node A' to 'Node G' are determined, the slot reservation section II has the highest priority according to the priority of the node given in the random access section I. The branch allocates a reserved slot from the node (s106). That is, the reserved slots in the slot reservation section II are sequentially allocated in a non-competitive manner by priority.

When the reserved slot is allocated, the 'node A' to 'node G' checks whether there is data to be transmitted (s108), and transmits a reservation message to reserve a transmission slot only when there is data to be transmitted (s110). ). If there is no data to be transmitted, the process of determining whether there is data to be transmitted by the node having the next priority is repeatedly performed.

When the reservation message is transmitted, only a node corresponding to the reserved transmission slot and a neighboring node receiving data from the node are activated to transmit and receive data (s112).

The process of steps 106 to 112 will be described by way of example.

First, 'Node A', which is determined to have the highest priority, allocates the first reserved slot through priority scheduling, and reserves a message to reserve a transmission slot (called 'first transmission slot') for transmitting actual data. Send it. At this time, since nodes 'Node B', 'C', and 'F', which are neighbor nodes of 'Node A', may receive a reservation message of 'Node A', 'Node B', 'C', and 'F' are themselves. When the transmission slot is reserved in the turn, it is recognized that the first transmission slot reserved by 'Node A' cannot be reserved. When the first transmission slot is reserved, only 'node A' corresponding to the first transmission slot and 'nodes B', 'C', and 'F' which are data receiving data from the 'node A' are activated. In other words, data transmitted from 'node A' is received by 'node B', 'C' and 'F'.

Next, when transmission of the reservation message of 'node A' is completed, 'node B' determined as the next priority of 'node A' reserves a second reservation slot, and a corresponding transmission slot (second transmission slot) Send a reservation message for booking. As described above, the 'node B' reserves one of the remaining transmission slots except for the first transmission slot reserved by the 'node A'. When the second transmission slot is reserved, only 'Node B' corresponding to the second transmission slot and only 'Node A' and 'Node D' which are neighbor nodes are activated, and data communication is performed with each other.

Next, when transmission of the reservation message of the 'node B' is completed, 'node F' determined as the next priority of the 'node B' reserves a third reservation slot, and a corresponding transmission slot (third transmission slot) Send a reservation message for booking. In this case, one of the remaining transmission slots is reserved except for the first and second transmission slots already reserved by the 'node A' and the 'node B'. When the third transmission slot is reserved, only 'node F' and neighbor nodes 'node A' and 'node G' corresponding to the third transmission slot are activated, and data communication is performed.

Of course, if there is no data to be transmitted by any node itself in the process as described above, the transmission process of the reservation message is omitted, and the sequence goes to the next node.

In such a manner, transmission slots are reserved for the remaining nodes, and data is communicated with neighbor nodes through the reserved transmission slots.

According to the embodiment of the present invention, priority is given to all nodes participating in the sensor network, and a slot for transmitting data is reserved through a slot reservation section in a non-competitive manner, and then transmitted through a transmission slot.

On the other hand, in the above embodiment, the random access interval (I) is described that is executed randomly only once in the initial driving of all nodes. This is because it assumes that all nodes are given priority only once. However, priority may not be given to all nodes by only one execution of the random access period (I). Therefore, the present invention can also apply to the random access interval I being executed until all nodes are given priority. Of course, even in this case, it may be considered to limit the information exchange process between nodes in the random access period (I) to within a certain number of times. That is, even in the continuous information exchange process, a node that is not given priority may occur. This is to prevent the unnecessary power consumption of the node because the node may be unnecessarily consumed when the random access period I is continued. The non-prioritized nodes do not participate in the network topology.

In addition, prioritization is possible in other ways. That is, after execution of the random access section (I), after a cycle consisting of the slot reservation section (II) and the data transmission section (III) is executed several times, the priority for each node (A to G) is automatically determined. Can be set again. As described above, it is necessary to reprioritize the node when an important message or urgent message occurs, or when a node is newly added or detached. Priority can be considered.

Although described with reference to the illustrated embodiment of the present invention as described above, this is merely exemplary, those skilled in the art to which the present invention pertains various modifications without departing from the spirit and scope of the present invention. It will be apparent that other embodiments may be modified and equivalent. Therefore, the true scope of the present invention should be determined by the technical idea of the appended claims.

1 is a Mac protocol structure diagram according to the prior art

2 is a structural diagram of a priority-based MAC protocol according to an embodiment of the present invention;

3 is a block diagram of the proposed underwater sensor network for explaining an embodiment of the present invention

4 is a configuration diagram of a state in which a priority is given to a node participating in the underwater sensor network of FIG.

5 is a flowchart illustrating a data transmission method in a sensor network to which a priority-based MAC protocol is applied according to an exemplary embodiment of the present invention.

Claims (8)

In the initial operation of all nodes participating in the sensor network, priorities for allocating reserved slot assignments for the nodes by priority scheduling while sharing the preset unique information of each node to neighboring nodes two hops apart. Forming a random access interval I giving? A slot reservation period for allocating a reservation slot from the node having the highest priority according to the priority given in the random access period (I) and transmitting the reservation message to reserve the transmission slot according to the presence or absence of data to be transmitted. Forming (II); And Forming a data transmission section (III) for transmitting data to the neighbor node through a transmission slot reserved by the reservation message; / RTI > If the priority is not given to some nodes in the random access period (I), the priority scheduling MAC protocol forming method, characterized in that by repeating the priority scheduling to be given to all nodes. The method of claim 1, The priority scheduling is to assign priority based on at least one of the unique ID of the node, the channel state of the node, the power state of the node, the remaining power of the node. delete The method of claim 1, The data transmission section (III) is a total sleep mode section, and the priority-based MAC protocol forming method, characterized in that only nodes for data transmission and reception in the transmission slot reserved through the reservation message becomes active. A first step of prioritizing nodes participating in the sensor network by the MAC protocol forming method according to any one of claims 1, 2, and 4; A second step of allocating a reservation slot from the node having the highest priority according to the priority, and transmitting a reservation message to reserve a transmission slot necessary for data transmission through the allocated reservation slot; And And a third step of performing data transmission / reception with the neighboring node through the transmission slot reserved by the reservation message. The method of claim 5, wherein the first step, A first step in which each node shares node information to neighboring nodes two hops away from itself according to a random access execution of the MAC protocol during initial startup of the node; And And a first and second steps of determining the priority of the nodes using the shared node information. The method of claim 5, wherein the second step, And transmitting the reservation message only when there is data to be transmitted among the nodes, in the sensor network to which the priority-based MAC protocol is applied. 8. The method of claim 7, In the sensor network to which the priority-based MAC protocol is applied, the neighbor node adjacent to the node that has transmitted the reservation message reserves only transmission slots other than the transmission slots reserved by the reservation message by the priority. Method of data transmission.

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