KR101006314B1 - Method for deciding period of information-exchange in wireless network - Google Patents

Abstract

A method of determining an information exchange cycle in a wireless network is provided. The method includes obtaining an update probability of an information exchange message in consideration of a moving speed of a node, and determining an information exchange period that is an exchange period of the information exchange message using the update probability. Considering the movement speed of the node, the information exchange interval of the information exchange message can be appropriately determined. Resource efficiency is improved by minimizing the exchange of information exchange messages between nodes. In addition, information exchange messages can be transmitted in a timely manner to optimally support network applications.

Description

Determination method of information exchange in wireless network {METHOD FOR DECIDING PERIOD OF INFORMATION-EXCHANGE IN WIRELESS NETWORK}

The present invention relates to a wireless network, and more particularly, to a method for determining an information exchange period in a wireless network.

Recently, with the development of information and communication technology, various wireless communication technologies have been developed. Wireless LAN (WLAN) is based on radio frequency technology, using a portable terminal such as a personal digital assistant (PDA), a laptop computer, a portable multimedia player (PMP), etc. It is a technology that allows wireless access to the Internet in a specific service area.

Since the Institute of Electrical and Electronics Engineers (IEEE) 802, the standardization body for WLAN technology, was established in February 1980, a number of standardization tasks have been performed. Early WLAN technology used 2.4 GHz frequency through IEEE 802.11 to support speeds of 1 to 2 Mbps for frequency hopping, spread spectrum, infrared communication, etc. Recently, Orthogonal Frequency Division Multiplex (OFDM) has been applied to up to 54 Mbps. Can support speed. In addition, IEEE 802.11 improves Quality for Service (QoS), access point protocol compatibility, security enhancement, radio resource measurement, and wireless access vehicular environment. Standards of various technologies such as, fast roaming, mesh network, interworking with external network, and wireless network management are being put into practice.

Wireless networks have limited computing power and network resources compared to wired networks. Wired networks have a fixed topology, while wireless networks are composed of nodes that do not have a fixed topology. The number of nodes and the connectivity between the nodes constituting the wireless network are not fixed. A node refers to a networking device participating in a wireless network. For example, the node may be a STA, an access point, a terminal, a wireless router, or the like. The upper level application program of the wireless network collects not only a radio link but also network state information, and shares necessary control and management information with the network or a counterpart communication program according to the collection result.

Due to the dynamically changing state of the wireless channel, wireless networks are more difficult to control and manage than wired networks. For control and management in a wireless network, each node must exchange information exchange messages with neighboring nodes. The exchange of information exchange messages between nodes shall not be affected by the mobility of the nodes. Information exchange messages need to be collected and transmitted without wasting unnecessary resources. The exchange of information exchange messages is transmitted periodically with different periods depending on the urgency of the information exchange messages. Hereinafter, the period for exchanging the information exchange message is called the information exchange cycle.

However, when the information exchange period is too short, network bandwidth is wasted due to frequent transmission and reception of information exchange messages. This results in inefficient use of limited network resources and interferes with actual data transmission. If the interval of information exchange is too long, each node does not properly receive the information exchange message, which causes problems in network management. For example, nodes are not properly supported for network applications running on higher layers. In addition, the wireless network topology configuration is not properly made. Since the wireless network system is a time variant system, the wireless network environment may change over time. When the information exchange cycle is fixedly used, an appropriate information exchange cycle may become inadequate according to the change of the wireless network environment.

Therefore, there is a need to provide an efficient information exchange cycle determination method in a wireless network.

An object of the present invention is to provide an efficient information exchange cycle determination method in a wireless network.

In one aspect, a method of determining an information exchange period in a wireless network is provided. The method includes obtaining an update probability of an information exchange message in consideration of a moving speed of a node, and determining an information exchange period that is an exchange period of the information exchange message using the update probability.

In another aspect, a method of information exchange message exchange in a wireless network is provided. The method may include obtaining an update probability of an information exchange message in consideration of a moving speed of a node, determining an information exchange period that is an exchange period of the information exchange message using the update probability, and the information according to the information exchange period. Exchanging an exchange message.

In another aspect, a node in a wireless network is provided. The node obtains an update probability of the information exchange message in consideration of the moving speed of the node, and uses the update probability to determine an information exchange period, which is an exchange period of the information exchange message, and the information exchange period obtained by the controller. And a transceiver for exchanging the information exchange message accordingly.

Considering the movement speed of the node, the information exchange interval of the information exchange message can be appropriately determined. Network resource waste can be reduced by minimizing the exchange of information exchange messages between nodes. In other words, it increases resource use efficiency by reducing unnecessary information provision. In addition, information exchange messages can be transmitted in a timely manner to optimally support network applications. That is, higher-level protocols or applications can be provided with the necessary information at the appropriate time. In addition, it is possible to improve the reliability of the topology configuration by ensuring the connectivity of the wireless network.

1 is a simplified illustration of a wireless network system.

Referring to FIG. 1, a wireless network system includes one or more basic service sets (BSSs). The BSS is a set of stations (STAs) that can successfully synchronize and communicate with each other, and is not a concept indicating a specific area. The BSS may be classified into an infrastructure BSS (Independent BSS) and an Independent BSS (IBSS). The infrastructure BSS is illustrated in FIG. 1. The infrastructure BSS (BSS1, BSS2) includes one or more STAs (STA1, STA3, STA4), an access point (AP) that is a STA that provides a distribution service, and a plurality of APs (AP1, AP2). Including a distribution system (DS) to connect the (). On the other hand, since the IBSS does not include an AP, all STAs are configured as mobile stations, and thus access to the DS is not allowed, thereby forming a self-contained network.

An STA is any functional medium that includes a medium access control (MAC) compliant with the IEEE 802.11 standard and a physical layer interface to a wireless medium. Broadly speaking, an AP and a non-AP station (Non- AP Station). The STA for wireless communication includes a processor and a transceiver, and includes a user interface and a display means. The processor is a functional unit designed to generate a frame to be transmitted through a wireless network or to process a frame received through the wireless network, and performs various functions for controlling a station. The transceiver is a unit that is functionally connected to the processor and is designed to transmit and receive frames over a wireless network for a station.

Among the STAs, the portable terminal operated by the user is a non-AP STA (STA1, STA3, STA4, STA6, STA7, STA8), which may simply refer to the non-AP STA. A non-AP STA may be a wireless transmit / receive unit (WTRU), a user equipment (UE), a mobile station (MS), a mobile terminal, or a mobile subscriber unit. It may also be called by other names.

The APs AP1 and AP2 are functional entities that provide access to the DS via a wireless medium for an associated station (STA) associated therewith. In an infrastructure BSS including an AP, communication between non-AP STAs is performed via an AP. However, when a direct link is established, direct communication between non-AP STAs is possible. The AP may be called a centralized controller, a base station (BS), a node-B, a base transceiver system (BTS), or a site controller in addition to the access point.

The plurality of infrastructure BSSs may be interconnected through a distribution system (DS). A plurality of BSSs connected through a DS is called an extended service set (ESS). STAs included in the ESS may communicate with each other, and a non-AP STA may move from one BSS to another BSS while communicating seamlessly within the same ESS.

The DS is a mechanism for one AP to communicate with another AP, which means that an AP transmits a frame for STAs coupled to a BSS managed by the AP or when one AP moves to another BSS. Frames can be delivered with external networks, such as wired networks. This DS does not necessarily need to be a network, and there is no limitation on its form as long as it can provide certain distribution services defined in IEEE 802.11. For example, the DS may be a wireless network such as a mesh network or a physical structure that connects APs with each other.

As shown in FIG. 1, a wireless network system including an AP is called an infrastructure network. Unlike infrastructure networks, wireless network systems that do not have a fixed infrastructure are called ad hoc networks. An ad hoc network is an autonomous and independent form of distributed nodes only. In an ad hoc network, a node communicates directly with a neighbor node without using an AP.

In an ad hoc network, the network topology changes from time to time depending on the node's movement pattern, traffic type, link quality or power margin. Therefore, in the ad hoc network, it is very difficult to set up a route and maintain the route to find a specific destination node. Since the mobile node has a limited radio transmission distance, information about the destination node is determined by neighboring nodes or intermediate nodes on the data transfer path. According to the movement pattern of nodes, a set of neighboring nodes capable of direct communication change together. Therefore, each node periodically broadcasts its existence and must maintain the aggregate information of neighboring nodes capable of direct communication at all times.

In a wired network, Internet routing protocols such as Routing Information Protocol (RIP) or Open Shortest Path First (OSPF) are used. Existing Internet routing protocols operate with periodic routing table management in a stable network environment with low liquidity. Existing Internet routing protocols require periodic message exchange, which wastes bandwidth and does not respond quickly to dynamic changes in the network. There is a lot of overhead to apply the existing Internet routing protocol to the ad hoc network. Therefore, a modification of an existing routing protocol or a new way of routing protocol is required to apply to an ad hoc network. The routing protocol applied to the ad hoc network is called ad hoc routing protocol.

The ad hoc routing protocol is currently being standardized by the Internet Engineering Task Force (IETF) Mobile Ad hoc NETwork (MANET) Working Group, which was formed in July 1997. Protocols such as Ad Hoc On-demand Distance Vector (AODV), Dynamic Source Routing (DSR), ZoneRouting Protocol (ZRP) and Temporally-Ordered Routing Algorithm (TORA) have been proposed as Internet drafts.

The ad hoc routing protocol may be classified into a hybrid method that is a combination of a proactive method and a reactive method, and a proactive method and a reactive method. In addition, ad hoc routing protocols can be classified by various criteria.

Proactive is a method of broadcasting routing information periodically or when the network topology changes. All nodes can always manage and maintain up-to-date routing information and route information. The proactive method has the advantage of enabling communication between nodes without delay in path discovery when traffic occurs. However, there is a big disadvantage in that the broadcast overhead of control information used for managing path information is large. Therefore, in order to reduce overhead, a method of minimizing the amount of control information has been studied. In addition, if an exchange period of control information is appropriately selected, overhead can be reduced and network performance can be improved. There is a table management routing protocol in a proactive manner.

Table management routing protocols include DSDV (Destination Sequenced Distance Vector), WRP (Wireless Routing Protocol), and CGSR (Clusterhead Gateway Switching Routing).

DSDV is based on the Bellman-Ford routing scheme used in wired networks. DSDV maintains route information in the routing table for each node. Route information maintained by each node may include a destination address, a metric, a sequence number, and a next hop. The sequence number is incremented when generating or updating new routing information. Use sequence numbers to prevent the occurrence of routing loops due to topology changes. Updating of the routing table takes the form of a full dump or an incremental dump. Pull dump is a method of broadcasting all routing information owned by a node to another node. Pull dump can be used when there is a lot of routing information to update. Incremental dumps only broadcast newly changed routing information. The destination address, metric, and sequence number of the route information is broadcast to the neighbor node through a full dump or incremental dump.

The reactive method is a method of searching for a route at the time when traffic occurs. The reactive method uses the information exchange method for route determination. The reactive method is a method capable of solving the overhead problem of control information of the proactive method. However, the reactive method causes a delay due to the initial path search. Therefore, the research of the reactive method is focused on minimizing the path search delay time as well as the optimal path search. Reactive management routing protocols include AODV and DSR.

AODV uses an information exchange method in the path partitioning that may occur due to interference or multi-path fading. By using the information exchange method, instead of resetting all the paths, only disconnected paths or required paths can be updated. The information exchange method minimizes network degradation due to full path discovery and speeds up recovery due to path loss. AODV, like DSDV, uses sequence numbers to prevent routing loops. In addition, AODV uses a route search procedure similar to DSR. If a route search is required in the AODV scheme, the source node generates a Route Request (RREQ) message and broadcasts the RREQ message to the neighbor node. When the intermediate node or the destination node with the route information to the destination node receives the RREQ message, it responds with a Routing Reply (RREP) message. The intermediate node or the destination node unicasts the RREP message in the opposite direction to the route through which the RREQ message was delivered. If the intermediate node does not have route information to the destination node, the intermediate node broadcasts the RREQ message back to the neighbor node. The node receiving the RREQ message generates and stores reverse route information. The node receiving the RREP message generates and stores forward route information. If a node receives the same RREQ message repeatedly, only the first received RREQ message is used. If an error occurs on a specific link within a route, perform a local route rescanning procedure, or send a Route Error (RERR) message to the source node. The source node receiving the RERR message performs the route rescanning procedure. The node that receives the RERR message deletes the route information associated with the failed link.

DSR is based on the source routing scheme. In DSR, every node maintains a root cache. The DSR consists of a route search procedure and a route management procedure. The route search procedure broadcasts an RREQ message to the neighbor node when there is no route information of the destination node when packet data is generated at the source node. When the route information to the destination node is not stored in the root cache of the intermediate node that receives the RREQ message, the RREQ message to which the intermediate node itself is added is broadcast again to the neighbor node. If route information to the destination node is stored in the root cache of the intermediate node that receives the RREQ message, the RREP message including the route information to the destination node is delivered to the source node. If an error occurs on a particular link within the route, a RERR message is sent to the source node. The node receiving the RERR message deletes the link information in error from its root cache. The node receiving the RRER message continues to deliver data using another bypass route. If there is no other bypass route, the node receiving the RRER message forwards the RERR message to the source node.

ZRP is a hybrid routing protocol that combines proactive and reactive methods. In ZRP, each node has a routing zone of a predefined range. The size of the routing area is defined based on the number of hops. Management of routing information in the same area is performed by the Intrazone Routing Protocol (IARP) based on the proactive method. The retrieval of route information to nodes belonging to the outer zone is performed by IERP (Interzone Routing Protocol) based on reactive method. And, BRP (Bordercasting Routing Protocol) is used for efficient broadcasting of IERP.

A wireless mesh network performs the function of a backbone network in a wireless network. The wireless mesh network is composed of a mesh router or relay, a fixed node or a mobility node. The mesh router / relay is connected directly or indirectly to the Internet to provide Internet services to nodes connected to the mesh router / relay. Nodes have multiple connections, not 1: 1 connections, with neighboring mesh routers / relays.

The substructure of the wireless mesh network may be an existing wireless technology IEEE 802.11a / b / g or a wireless sensor network, a wired LAN structure. In addition, the wireless mesh network may have a form connected to the Internet through a plurality of gateways in order to improve the performance of the network. Each node of the wireless mesh network must maintain a connection with an Internet gateway or select an optimal connection when there are multiple connections. To do this, the node must locally collect link state information and network topology configuration information and broadcast the collected information within the network.

The wireless mesh network searches for a configurable network topology of nodes participating in the network. Based on the search results, the wireless mesh network performs a network topology configuration process to improve network bandwidth or optimize transmission power consumption. The network topology configuration is based on neighbor discovery information collected through periodic information exchange messages. In addition, after the network topology configuration is completed, the network link status must be collected, and information exchange messages must be continuously transmitted and received to confirm that the routing node or target nodes are alive.

Network Topology Control (TC) aims to improve network-wide performance by reducing unnecessary collisions and interferences between nodes while maintaining network connectivity in wireless networks. Network topology control begins by knowing and collecting the status of neighboring nodes present in the communication area. The collection of information about these neighboring nodes is accomplished by sending periodic information exchange messages. Information exchange messages are also referred to as hello messages. The information exchange message includes an ID (IDentifier) of the node, location information and routing table information. The node can know the relative position with the neighbor nodes, link state information, network configuration information, etc. through the information exchange message.

The information exchange message includes link state data, control information, network management data, and the like. The link state information is for topology configuration or routing path establishment of a wireless network. The link state information is for topology configuration or routing path setting, and includes signal to noise ratio (SNR), network bandwidth, and delivery ratio. The control information is for controlling network protocol operation or service components, and there are topology control, routing table, and the like. Network management information is information determined by a network management program or application. In addition, information exchange messages can be defined and used in a wide variety of ways. For example, the communication quality of service control information is for supporting multimedia data and is transmitted to nodes on a path periodically or when changing control values. Network management programs also pass network control factors to the nodes on the path. The network control factor is information necessary for network management based on information collected from network nodes.

As such, each node in a wireless network can exchange information exchange messages to ensure accurate network connectivity and support network applications. However, the exchange of information exchange messages consumes network resources and node resources. In addition, due to the mobility of the nodes, the number, relative position, and connectivity of the network nodes change, so that an appropriate information exchange period must be determined.

Hereinafter, a method of determining an optimal information exchange period in a wireless network will be described.

2 illustrates an example in which a node moves in a wireless network to form a new network topology.

Referring to FIG. 2, the first to fifth nodes 1, 2, 3, 4, and 5 do not move, but the X-th node X moves. Before the X-th node X moves, the X-th node X is connected to the second node 2 and the third node 3 which are neighboring nodes. The Xth node X exchanges an information exchange message with a neighbor node according to an information exchange cycle. Through the information exchange message, the X-th node X may maintain connection with the second node 2 and the third node 3 even after the movement. That is, due to the movement of the X-th node X, a new network topology is constructed.

3 illustrates an example in which a node moves in a wireless network and the network is partitioned.

Referring to FIG. 3, the first to fifth nodes 1, 2, 3, 4, and 5 do not move, but the X-th node X moves. Before the X-th node X moves, the X-th node X is connected to the second node 2 and the third node 3 which are neighboring nodes. After the X-th node X moves, the X-th node X is disconnected from the third node 3. That is, the network is divided due to the movement of the X-th node X. As such, due to the movement of the nodes, the network topology changes, and thus, connectivity may not be guaranteed, thereby causing a situation in which the network is partitioned. As the mobility of nodes increases, such partitioning may occur more frequently.

The reason why the network is split due to the movement of the node is that the moving node does not properly provide its information to neighboring nodes. If a node moves at a faster rate than the information exchange period, the node may not properly send an information exchange message to its neighbors. In this case, the node cannot lose network connectivity. Neighbors will not be able to gather the necessary information and will not be able to deliver network applications. If the node is moving slowly, there is no need to send information exchange messages in a fast cycle. If the information exchange message is exchanged at regular intervals even though the movement speed is slow, network bandwidth is wasted by repeatedly transmitting the same information to neighboring nodes. As the information exchange message is delivered to the network, each node consumes computation and memory resources, uses network bandwidth, and may cause collisions or interference with general data transmission. In addition, if individual nodes fail to take advantage of fair and legitimate network bandwidth using inaccurate or late timing information compared to other nodes in the network, a particular node may not be able to monopolize network resources or pass information. do.

As such, the information exchange cycle affects the resource consumption and function of the entire wireless network. The information exchange cycle enables each node to accurately identify neighboring nodes that are out of transmission range or nodes newly included in the transmission range, thus directly affecting network topology configuration and network connectivity. Therefore, it is necessary to determine the information exchange cycle of the information exchange message by reflecting the movement speed of the node, and adjust the information exchange cycle.

Hereinafter, a method of determining an information exchange period when each node updates neighbor node information in a wireless network is illustrated, but the present invention can also be applied when exchanging various other information exchange messages.

4 illustrates a case where a node moves into a transmission range outside the transmission range of another node due to the movement of the node. The transmission range of a node is a circle around the node. The transmission range of a node can be divided into four sectors.

Referring to FIG. 4, node C, which was outside the sector of node A, moves and enters the sector of node A. FIG. Node A has node B information as the nearest nearest neighbor node information before node C moves. The nearest neighbor information is used for ad hoc routing or network topology construction. Node A may communicate with other nodes using the nearest neighbor node information.

If node C is closer to node A than node B due to the movement of node C, node A needs to update the nearest neighbor node information. If a path AC occurs shorter than the length of path AB, then an information exchange message needs to be sent. In this case, it may also be considered when the transmission power is controlled.

FIG. 5 is a diagram for explaining a probability of entering a transmission range outside a transmission range of another node due to the movement of a node. FIG. 6 is a view embodying FIG. 5.

5 and 6, the circle around node C is a moving range in which node C can move randomly. The radius of the circle around node C is determined by the speed of node C's movement. This is because the travel distance is the product of the travel time and the travel speed. The area S is a portion where a sector of the node A and a circle centering on the node C overlap. When node C moves randomly and enters the area S, the nearest neighbor node of node A is changed from node B to node C. Node A needs to update the neighbor node information.

The probability (P _join ) at which node C enters area S and node N updates neighboring node information can be expressed by the following equation.

Where S is the area of the area S and r ₂ is the radius of the circle around node C.

The area S can be divided into a node S ₂ and an area S ₁ close to the node C. The area S ₁ of the area S ₁ and the area S ₂ of the area S ₂ are equal to the area of the fan shape minus the area of the isosceles triangle. S ₁ and S ₂ can be expressed as the following equation.

Where r ₁ is the radius of a circle centered on node A, the transmission range of node A, r ₂ is the radius of a circle centered on node C, and ℓ ₁ is the length of a circular arc centered on node A ℓ ₂ is the length of a circular arc of a fan shape centering on node C, θ ₁ is a cabinet of a fan shape centering on node A, and θ ₂ is a cabinet of a fan shape centering on node C. r ₂ is determined by the moving speed of node C.

The area S of the area S can be expressed by the following equation.

As described above, the probability when the node that needs to update the nearest neighbor node information from each node of the wireless network moves in can be defined as in Equation 1.

Next, even if the node moves out of the transmission range within the transmission range of another node, it is necessary to update the nearest neighbor node information.

7 illustrates a case where the node moves out of the transmission range within the transmission range of another node due to the movement of the node.

Referring to FIG. 7, when Node B, which was at the most recent distance based on Node A, moves to the B 'position, Node B loses the qualification of Node A's nearest distance neighbor. The closest neighbor node of node A changes from B to C. Therefore, Node A needs to update the nearest neighbor node information. The nearest neighbor node information can be updated through the exchange of information exchange messages.

8 is a diagram for explaining a probability of moving out of a transmission range within a transmission range of another node due to the movement of a node. FIG. 9 is a view embodying FIG. 8.

8 and 9, the circle around Node B is a moving range in which Node B can move randomly. The radius of the circle around node B is determined by the speed of node B's movement. The area S is a portion where the sectors of the node A and the circle around the node B do not overlap. When node B moves randomly and enters area S, node A's nearest neighbor node is changed from node B to node C. Node A needs to update the neighbor node information.

The node B to the node A enters the area S is the probability (P _leave) to update the neighboring node information can be expressed by the following mathematical expression.

The probability (P _join ) at which node C enters area S and node N updates neighboring node information can be expressed by the following equation.

Here, S is the area of the area S, r ₂ is the radius of the circle around the node B is r ₂ .

The sector centering on node B is called area S ₁ . The area S ₁ may be divided into an area S, an area S _2, and an area S ₃ .

The area S ₁ may be represented as in the following equation.

Here, r ₂ is the radius of the circle centered on the node B, and ℓ ₂ is the length of a circular arc centered on the node B.

The area S ₂ is equal to the sectoral sector centered on node A minus the isosceles triangle with node A as the vertex. The area S ₂ of the area S ₂ may be expressed by the following equation.

Where r ₁ is the radius of a circle around node A, the transmission range of node A, l ₁ is the length of a circular arc around node A, and θ ₁ is a fan-shaped cabinet around node A to be.

The area S ₃ is the area of the isosceles triangle with node B as the vertex. The area S ₃ of the area S ₃ may be expressed by the following equation.

Here, r ₂ is the radius of a circle centered on node B, and θ ₂ is a fan-shaped cabinet centered on node B. r ₂ is determined by the moving speed of Node B.

Region S is the same as region S ₂ and region S ₃ in region S ₁ . The area S of the area S can be expressed by the following equation.

The probability (P _join ) at which Node A updates neighbor node information due to the movement of Node B or Node C described so far has been assumed assuming that Node A is fixed.

Hereinafter, consider the case where node A moves. If node A moves, consider the Doppler Effect.

10 shows a case where two nodes move.

Referring to FIG. 10, node A moves to position A ′ and node C moves to position C ′. The vector r _A represents the moving distance and the moving direction of the node A, and the vector r _C represents the moving distance and the moving direction of the node C. The vector r _A is determined by the moving speed of node A, and r _C is determined by the moving speed of node C. Vector r _A and vector r _C can be divided into x component which is a horizontal component and y component which is a vertical component, respectively.

The relative x component D _x of the vector r _A and the vector r _C can be expressed _by the following equation.

Where r _A is the magnitude of the vector r _A , r _C is the magnitude of the vector r _C , α _A is the absolute angle when moved to position A 'of node A, and α _C is moved to position C' of node C Absolute angle of the hour. That is, α _A means an angle between the vector r _A and the x axis, and α _C means an angle between the vector r _C and the x axis.

Size r _n of a vector r _n on the node n can be expressed as the following mathematical expression.

Where V _n is the moving speed of node n and t is the moving time of node n.

The relative y component D _y of the vector r _A and the vector r _C can be expressed by the following equation.

Hereinafter, D is defined as follows.

When a plurality of nodes are moved respectively, it can be considered to be divided into (1) approaching each other, (2) moving away from each other, (3) moving in the same direction.

When the node A and the node C approach in a direction facing each other, the probability that the node A updates the neighboring node information is called P _app and can be expressed as the following equation.

Where r _k is the absolute distance between node A and node C. r _k is calculated as Geometric Distance.

When the node A and the node C are far from each other, the probability that the node A updates the neighboring node information is called P _away , and can be expressed by the following equation.

When node A and node C move in the same direction, a probability that node A updates neighboring node information is _referred to as P _follow , and may be expressed as in the following equation.

Here, the first term P _f1 is faster than the preceding node, so that Equation 12 approaches in the direction facing each other, and the second term P _f2 is the velocity of the subsequent node than the preceding node. Is slow and away from Equation (13).

Accordingly, the node A and the node C correct the probability P _app when coming toward each other, the node A may indicate a probability P _'app to update the neighbor node information, such as the following mathematical expression.

When node A and node C move away from each other, the probability P _away may be corrected so that P ' _away for updating the neighbor node information by node A may be expressed as in the following equation.

The information exchange period can be defined using the probability that each node of the wireless network described so far updates the neighbor node information. The information exchange cycle may be referred to as an update cycle of neighbor node information.

Probability when information exchange is required may be referred to as P _change and expressed as the following equation.

Probability P _change when information exchange is needed includes the probability of all cases of updating neighboring node information.

The information exchange period (t _periodic ) can be expressed by the following equation using the probability P _change when information exchange is required.

Here, P _th is a threshold indicating a criterion for determining movement, V _n is a moving speed of node n, and α and β are coefficients.

FIG. 11 illustrates a case where a node moves into a transmission range outside of a transmission range of another node using a directional antenna due to the movement of the node.

Referring to FIG. 11, node A uses a directional antenna so that a transmission area has a specific range of directionality. Node C, which was outside the transport zone of Node A, moves and enters the transport zone of Node A. Node A has node B information as the nearest nearest neighbor node information before node C moves. If node C is closer to node A than node B due to the movement of node C, node A needs to update the nearest neighbor node information. FIG. 4 shows the transmission area of A divided into sectors, and FIG. 11 limits the transmission area to a specific range. Therefore, even when using a directional antenna, the information exchange period described so far can be applied directly.

12 is a graph illustrating an information exchange cycle according to a moving speed of a node. The graph x-axis is the speed of movement of the node (v), and the graph y-axis is the period of information exchange (Period). The unit of travel speed is m / s (meter per second), and the unit of information exchange period is second.

Referring to FIG. 12, the faster the movement speed of a node, the shorter the information exchange period. The information exchange cycle according to the movement speed of the node has a threshold value P _th , which represents a criterion for determining movement, from 0.1 to 0.5, in units of 0.1. It depends on the change. The larger the threshold, the longer the information exchange cycle according to the moving speed.

As described above, by determining the information exchange period in consideration of the moving speed of each node in the wireless network, it is possible to efficiently exchange information between nodes.

In a wireless network composed of a plurality of nodes, the node determines its movement speed, and then determines the information exchange cycle by calculating the transmission range of the node itself and the transmission range of the neighbor node according to the movement speed of the node. Through the determined information exchange period, the node can provide the node's own location information to neighboring nodes within the transmission range. The movement speed of the node itself can be determined using a device that can know the relative or absolute position of the node itself. This is not a centralized algorithm but a distributed algorithm.

The method of determining the information exchange cycle described so far may be used when not only data link or network protocols, but also any protocol or network application used in a wireless network needs network state information or control information. The information exchange period determination method may be applied when exchanging information exchange messages necessary to provide network connectivity or detailed communication service quality in various wireless networks such as an ad hoc network and a wireless mesh network.

Considering the movement speed of the node, the information exchange interval of the information exchange message can be appropriately determined. Network resource waste can be reduced by minimizing the exchange of information exchange messages between nodes. In other words, it increases resource use efficiency by reducing unnecessary information provision. In addition, it is possible to optimally support network application programs by transmitting control information, status information, management information, and the like in a timely manner. That is, higher-level protocols or applications can be provided with the necessary information at the appropriate time. In addition, it is possible to improve the reliability of the topology configuration by ensuring the connectivity of the wireless network.

All of the above functions may be performed by a processor such as a microprocessor, a controller, a microcontroller, an application specific integrated circuit (ASIC), or the like according to software or program code coded to perform the function. The design, development and implementation of the code will be apparent to those skilled in the art based on the description of the present invention.

Although the present invention has been described above with reference to the embodiments, it will be apparent to those skilled in the art that the present invention may be modified and changed in various ways without departing from the spirit and scope of the present invention. I can understand. Therefore, the present invention is not limited to the above-described embodiment, and the present invention will include all embodiments within the scope of the following claims.

1 is a simplified illustration of a wireless network system.

2 illustrates an example in which a node moves in a wireless network to configure a new network topology.

3 illustrates an example in which a node moves in a wireless network and the network is divided.

4 illustrates a case where a node moves into a transmission range outside the transmission range of another node due to the movement of the node.

FIG. 5 is a diagram for explaining a probability of entering a transmission range outside a transmission range of another node due to the movement of a node.

FIG. 6 is a view embodying FIG. 5.

7 illustrates a case where the node moves out of the transmission range within the transmission range of another node due to the movement of the node.

8 is a diagram for explaining a probability of moving out of a transmission range within a transmission range of another node due to the movement of a node.

FIG. 9 is a view embodying FIG. 8.

10 shows a case where two nodes move.

11 illustrates a case where a node moves into a transmission range outside of a transmission range of another node using a directional antenna due to the movement of the node.

12 is a graph illustrating an information exchange period with respect to a moving speed of a node.

Claims (11)

In the information exchange cycle determination method in a wireless network, Obtaining an update probability of the information exchange message in consideration of the moving speed of the node; And And determining an information exchange cycle which is an exchange cycle of the information exchange message using the update probability. The method of claim 1, Wherein the update probability is a probability that the node enters into a transmission range of a neighboring node or a probability that the node goes out of a transmission range of a neighboring node. The method of claim 1, The update probability P _change is

Information exchange cycle determination method, characterized in that. Here, r ₂ is the radius of the circle around the node in consideration of the moving speed, and when the update probability is a probability that the node enters the transmission range of the neighboring node, S is the transmission range and the circle. If the area of overlapping area and the update probability is the probability that the node is out of the transmission range of the neighboring node, S is the area of the area where the transmission range and the circle do not overlap. The method of claim 1, The update probability is determined by considering the Doppler effect due to the relative movement of the node and the neighbor node further. The method of claim 1, The information exchange period t _periodic is

Information exchange cycle determination method, characterized in that. Where P _th is a threshold indicating a criterion for determining the movement of the node, V _n is the movement speed, and α and β are coefficients. The method of claim 1, And exchanging the information exchange message according to the information exchange cycle. The method of claim 1, And the information exchange message is one of link state information, control information, and network management information. The method of claim 1, And wherein said wireless network is an infrastructure network or an ad hoc network. In the information exchange message exchange method in a wireless network, Obtaining an update probability of the information exchange message in consideration of the moving speed of the node; Determining an information exchange cycle which is an exchange cycle of the information exchange message using the update probability; And Exchanging the information exchange message in accordance with the information exchange cycle. The method of claim 9, And the information exchange message is one of link status information, control information, and network management information. A control unit which obtains an update probability of the information exchange message in consideration of a moving speed of the node, and determines an information exchange period that is an exchange period of the information exchange message using the update probability; And And a transceiver for exchanging the information exchange message according to the information exchange cycle obtained by the control unit.

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