WO2008096909A1

WO2008096909A1 - Method for routing a path setting in a wireless sensor network and apparatus for performing the same

Info

Publication number: WO2008096909A1
Application number: PCT/KR2007/000591
Authority: WO
Inventors: Ki-Hyung Kim; Chae-Seong Lim; Waleed Mansoor
Original assignee: Ki-Hyung Kim; Chae-Seong Lim; Waleed Mansoor
Priority date: 2007-02-04
Filing date: 2007-02-04
Publication date: 2008-08-14
Also published as: KR20100004971A; KR101055416B1

Abstract

An apparatus for setting a routing path includes a logical processing part, a hardware processing part and an antenna. The logical processing part includes a sensing device and a memory. The hardware processing part includes a neighbor node information managing module that manages a neighbor node. The antenna wirelessly connects to an external node and the hardware processing part. The logical processing part and the hardware processing part finally receive a packet from the external node in a destination node operation, and search for a first neighbor nodes in a source node operation, to transmit the packet to the nearest node of the destination node of the first neighbor node when the destination node is not included in the first neighbor node. Therefore, it may be possible to perform hierarchical routing by using a short address dynamically assigned thereto in a wireless sensor network.

Description

METHOD FOR ROUTING A PATH SETTING IN A WIRELESS SENSOR NETWORK AND APPARATUS FOR PERFORMING THE

SAME

Technical Field

The present invention relates to a method for setting a routing path and an apparatus for performing the routing path setting method, and more particularly, to a method for setting a routing path in a wireless sensor network and an apparatus for performing the routing path setting method.

Background Art

A general mobile telecommunication system receives and transmits data between a mobile element and a base station. The mobile element and the base station receive and transmit data, not via other mobile elements or nodes, but directly. However, a sensor network uses other sensor nodes when transmitting data of a sensor node to a sink node.

The structure of a general sensor network will be described with reference to FIG. 1. As shown in FIG. 1, the sensor network has a sink node and a plurality of sensor nodes. Although FIG. 1 shows only one sink node, the sensor network can be composed of 2 or more sink nodes.

The sensor node collects data on target areas set by a designated user. Information on target areas collected by the sensor node may include, for example, ambient temperature or humidity, object movement, and gas leakage.

The sensor node transmits data of collected information at the target area to the sink node. The sink node receives data sent by sensor nodes of the sensor network. A sensor node within a predetermined distance of the sink node directly transmits data to the sink node. However, a sensor node that is beyond a predetermined distance transmits collected data to the adjacent sensor nodes, instead of directly sending the data to the sink node. As described above, a sensor node that is not within a predetermined distance transmits data using adjacent sensor nodes, to minimize power consumption for data transmission. That is, the distance between the sink node and the sensor node, and the power needed for the sensor node to transmit data to the sink node, are generally proportional to each other.

Accordingly, a sensor node that is not within a predetermined distance from the sink node transmits collected data using a plurality of sensor nodes, to minimize power consumption required for data transmission. Hereinafter, a node performing a role of relaying data of another sensor node will be referred to a relay node. Alternatively, the relay node may also transmit self-collected data to the sink node using another relay node or directly.

As described above, the sensor node collects information of a target to deliver to the sink node. Generally, the target node and the sink node are not fixed, and may be in a mobile state. FIG. 2 is a schematic diagram illustrating a target that is moving in a wireless sensor network. In FIG. 2, temperature information regarding a predetermined area is transferred to a moving car and so on. Thus, the moving car may receive the temperature information regarding the predetermined area in real-time. FIG. 3 is a schematic diagram illustrating a sink node that is moving in a wireless sensor network. In FIG. 3, information regarding a moving object is transferred to the sink node.

FIG. 4 is a schematic diagram illustrating a process that sets a routing path in a wireless sensor network. Hereinafter, a process in which the first sensor node ' 1 ' sets a routing path as a sink node will be described using FIG. 4. The first sensor node T generates a routing request (RREQ) message including information such as its own address (or a source address) and a sink node address (or a destination address). The first sensor node ' 1 ' broadcasts the generated RREQ message to adjacent sensor nodes.

In FIG. 4, sensor node '2', a fourth sensor node '4' and a fifth sensor node '5' receive the RREQ message. The sensor nodes receiving the RREQ message compare a destination address with their own addresses. When the destination address and their own addresses are different from each other, the sensor nodes renews the received RREQ message to broadcast to adjacent nodes. The renewed information includes a hop count.

Moreover, the sensor node receiving the RREQ message generates a routing table using the received RREQ message. The routing table may include a source node address, a destination node address, the hop count, a sensor node address that broadcasts the RREQ message, etc. The RREQ message broadcasted by the first sensor node ' 1 ' is transferred to the sink node via various paths. The sink node sets a routing path using the hop count included in the transferred RREQ message. That is, the sink node sets a routing path as a short path that has the smallest hop count. Therefore, the sink node transfers a routing reply (RREP) message to the fourth sensor node '4'. The fourth sensor node '4' transfers the RREP message to the first sensor node T using a routing table that is stored therein. As the above-described processes are performed, a routing path is set between the first sensor node ' 1 ' and the sink node. The first sensor node ' 1 ' transfers collected information to the sink node using the routing path.

Disclosure of the Invention

Technical Problem

The present invention provides a method for setting a routing path in a wireless sensor network having a short path using adjacent node information to transfer a packet.

The present invention also provides an apparatus for performing the method in the above-mentioned wireless sensor network.

Technical Solution

In one aspect of the present invention, there is provided a method for setting a routing path in a wireless sensor network transferring a packet between a source node and a destination node. The method comprises: (a) searching for a neighbor node of the source node as the routing is started; (b) transferring a packet to the destination node when the destination node is included in the neighbor nodes, and finishing the routing; (c) searching for the nearest node to the destination node of the neighbor nodes, when the destination node is not included in the neighbor nodes, to transmit a packet to the nearest node; and (d) searching for neighbor nodes, which is performed by the nearest node, to feedback to step (b). In one embodiment, a hop count for the packet transfer may be less than a hop count for hierarchically connecting to the source node and the destination node.

In one embodiment, the neighbor nodes may be obtained from a neighbor table of the source node. In another aspect of the present invention, there is provided a method for setting a routing path in a wireless sensor network. The method comprises: (a) setting a current node, a destination node and the next hop node that is nearest to the current node and the destination node; (b) calculating a first hop distance in a hierarchical routing path from the current node to the destination node and a second hop distance in a hierarchical path from the next hop node nearest to the destination node; (c) setting the next hop node in a hierarchical routing path; (d) querying a neighbor table to extract neighbor node information from the neighbor table; (e) calculating a third hop distance in a hierarchical routing path from the neighbor node to the destination node; (f) comparing the first hop distance with the third hop distance; (g) checking whether or not the whole search for a neighbor table has ended, when the first hop distance is less than or equal to the third hop distance; (h) feeding back to step (d) when the whole search for a neighbor table has not ended, and transferring a packet to the next hop node when the whole search for a neighbor table has ended; (i) comparing the second hop distance with the third hop distance when the first hop distance is greater than the third hop distance; and (j) setting the searched neighbor node as the next hop node to feedback to step (g), when the second hop distance is greater than the third hop distance. In still another aspect of the present invention, an apparatus for setting a routing path in a wireless sensor network includes a destination node, a source node and the next hop node. The destination node finally receives a packet. The source node searches for a plurality of first neighbor nodes as a routing for transmitting a packet is started and transmits a packet to the nearest node of the destination node of the first neighbor nodes when the destination node is not included in the first neighbor nodes. The next hop node searches for a plurality of second neighbor nodes as a packet is received from the source node and transmits the packet to the destination node or the nearest node of the destination node of the second neighbor nodes. In one embodiment, the source node may transmit a packet to the destination node when a destination node is not included in the neighbor nodes.

In one embodiment, each of the destination node and the source node may be one.

In one embodiment, the next hop distance may be no more than one. In one embodiment, a hop count for the packet transfer may be less than a hop count for hierarchically connecting to the source node and the destination node.

In one embodiment, the neighbor nodes may be obtained from a neighbor table of the source node. In further still another aspect of the present invention, an apparatus for setting a routing path in a wireless sensor network include a logical processing part, a hardware processing part and an antenna. The logical processing part includes a sensing device and a memory. The hardware processing part includes a neighbor node information managing module that manages a neighbor node using a neighbor table stored in the memory. The antenna wirelessly connects to an external node and the hardware processing part. Here, the logical processing part and the hardware processing part finally receive a packet from the external node in a destination node operation, and search for a first neighbor nodes in a source node operation, to transmit the packet to the nearest node of the destination node of the first neighbor node when the destination node is not included in the first neighbor node.

In one embodiment, the logical processing part and the hardware processing part may search for a plurality of second neighbor nodes based on a packet from the source node when the next hop node is operated, and transmit the packet to the destination node or the nearest node of the destination node of the second neighbor nodes.

Advantageous Effects

As described above, according to the present invention, it is possible to perform hierarchical routing by using a 16-bit short address that is dynamically assigned thereto in a wireless sensor network, for example, a low-power wireless personal area network (LoWPAN) based on Internet Protocol version 6 (IPv6)

(6LoWPAN). For example, in a wireless sensor network, hierarchical routing is perfoπned by using neighbor node information, and the nearest node adjacent to a destination node receiving a packet is searched for to transmit the packet, so that the hop count according to a packet transmission may be decreased.

Furthermore, the total hop count for hierarchical routing is decreased, so that a routing time that is required for transmitting a packet may be decreased.

Furthermore, the total hop count is decreased, so that the traffic generated in the routing operation may be decreased and the power consumption of the nodes may be decreased.

Brief Description of the Drawings

The above and other advantages of the present invention will become more apparent by describing in detail example embodiments thereof with reference to the accompanying drawings, in which:

FIG. 1 is a schematic diagram illustrating the structure of a wireless sensor network; FIG. 2 is a schematic diagram illustrating a target that is moving in a wireless sensor network;

FIG. 3 is a schematic diagram illustrating a sink node that is moving in a wireless sensor network;

FIG. 4 is a schematic diagram illustrating a process that sets a routing path in a wireless sensor network;

FIG. 5 is a schematic diagram illustrating the structure of a wireless sensor network that is used in the present invention;

FIG. 6 shows an example of a wireless sensor network protocol stack that is suited to the present invention; FIG. 7 is a figure of a header format of the conventional Internet Protocol version 6 (IPv6);

FIG. 8 shows an example of a media access control (MAC)/physical (PHY) layer data frame format as shown in FIG. 6;

FIG. 9 is a schematic diagram illustrating a multi-hop tree according to the present invention;

FIG. 10 is a block diagram illustrating a sensor node performing a method for setting a hierarchical routing path according to the present invention;

FIG. 11 is a schematic diagram illustrating a method for assigning an address according to an exemplary embodiment of the present invention; FIG. 12 is a schematic diagram illustrating a method for setting a routing path using an address assigning method of FIG. 11 ;

FIGS. 13 and 14 are schematic diagrams illustrating a method for setting a routing path according to another exemplary embodiment of the present invention; and FIG. 15 is a flowchart illustrating a method for setting a hierarchical routing path according to another exemplary embodiment of the present invention.

Best Mode for Carrying Out the Invention

It should be understood that the example embodiments of the present invention described below may be varied modified in many different ways without departing from the inventive principles disclosed herein, and the scope of the present invention is therefore not limited to these particular following embodiments. Rather, these embodiments are provided so that this disclosure will be through and complete, and will fully convey the concept of the invention to those skilled in the art by way of example and not of limitation.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. Prior to describing the preferred embodiments, the following definitions are provided to clarify terms used throughout this specification.

- A current node represents a predetermined node, that is, an Institute of Electrical and Electronics Engineers (IEEE) 802.15.4 device receives an Internet Protocol version 6 (IPv6) packet in a wireless sensor network. - A depth represents a hop distance between a coordinator of a wireless sensor network and a predetermined device. For example, the depth of the coordinator may be zero.

- A maximum number of children (MC) represents the maximum number of children that a predetermined device (i.e., a node) can have. - A neighbor table represents a table having information of a plurality of neighboring devices within a personal operating space (POS). The neighbor table includes a plurality of fields such as a personal area network ID (PAN ID: 16 bits), a neighbor short address (Neighbor.16-bit short address: 16 bits), an EUI-64 address of a neighbor (Neighbor.IEEE EUI 64-bit address: 64 bits), a neighbor device type (Neighbor.Device type: 2 bits), a neighbor relationship (Neighbor.Relationship: 2 bits), a neighbor depth (Neighbor .Depth: 8 bits), etc. In the neighbor table, when the field of the neighbor device type is OO', Ol ' and ' 10', the neighbor device may be a coordinator, a router and an end device, respectively. A field of the neighbor device type which corresponds to ' 11 ' is reserved. In the neighbor table, when the field of the neighbor relationship is OO' and Ol ', the neighbor device may be a parent node, and a child node, respectively. A field of the neighbor relationship corresponding to ' 10' and ' 11 ' is reserved. - A personal area network identification (PAN ID) represents a wireless sensor network 16-bit identifier for managing. Here, a POS represents an area within a sensing range of a wireless transmission of an IEEE 802.15.4 packet.

- A reduced-function device (RFD) represents an IEEE 802.15.4 device of a wireless sensor network having not a routing function. The RFD does not transfer a plurality of IPv6 packets to the next hop device. That is, the RFD only performs as an end device in a wireless sensor network.

- A router represents a full-function device (FFD) capable of routing a packet to the next hop device in a wireless sensor network, and a short address is a 16-bit address that is dynamically assigned to a device from a parent node. A wireless sensor network based on IPv6 that is suitably adapted to the present invention will be described in FIG. 5. In this exemplary embodiment, the wireless sensor network may be a low-power wireless personal area network (which will be referred to as "LoWPAN").

FIG. 5 is a schematic diagram illustrating the structure of a wireless sensor network that is used in the present invention.

Referring to FIG. 5, a wireless sensor network includes one PAN coordinator 10, a plurality of routers 20a, 20b and 20c and a plurality of terminal devices 30a, 30b, 30c, 3Od and 30e.

According to the IEEE 802.15.4 standard, the wireless sensor network devices include a full-function device (which will be referred to as an FFD device) that realizes a full protocol set of the IEEE 802.15.4 standard, and a reduced- function device (which will be referred to as an RFD device) not having a function of a router. For example, the PAN coordinator 10 and the routers 20a, 20b and 20c may be the FFD device, and the terminal devices 30a, 30b, 30c, 30e and 30e may be the RFD device.

The FFD may support almost all network types that are supported in the IEEE 802.15.4 standard, and may transmit and receive a packet between the FFD and the RFD. The FFD may perform the role of a PAN coordinator, and may perform almost all functions that are described in the IEEE 802.15.4 standard.

On the other hand, the RFD is designed to be suitable for a small and light device. The RFD may minimize an energy consumption ratio due to simple functions and simple operation, and minimize resource usage to reduce chip manufacturing costs so that the cost of the device may be decreased. The RFD may be used for an end device in all network types. That is, the RFD does not have a routing function, so that it means that the RFD cannot transfer peer-to-peer data and the RFD cannot perform the role of a PAN coordinator.

A star topology configured by an RFD and an FFD may solve inefficient wireless interfaces, such as home networks, personal computer (PC) peripheral devices, toys, game devices, health-related machines, etc. Peer-to-peer communication may utilize an ad-hoc routing function that is provided from a network layer. That is, the peer-to-peer communication may be applied to a sensor network, remote control, an actuator and so on. A plurality of devices of a wireless sensor network according to the IEEE

802.15.4-2003 standard are connected to each other as a parent device and a child device in a wireless sensor network. The child device is dynamically assigned a 16-bit short address from a parent device through an association.

That is, an IEEE 802.15.4 device may be dynamically assigned a 16-bit short address during an association operation with an adjacent device (or a router) that is to be a parent device. Communication between a parent and a child may be made possible through the assigned short address. A disassociation is a process in which an association with an adjacent device is removed.

A PAN coordinator 10 is an FFD, which is a main manager of a wireless sensor network, may initiate a synchronization of an entire wireless sensor network by transmitting a beacon.

The terminal devices 30a, 30b, 30c, 3Od and 30e are connected to one of the routers 20a, 20b and 20c to communicate to another terminal device connected to the corresponding router. The routers 20a, 20b and 20c route a packet received from at least one of the terminal devices 30a, 30b, 30c, 30d and 30e or another router in accordance to a hierarchical routing path setting method of the present invention. FIG. 6 shows an example of a wireless sensor network protocol stack that is suited to the present invention.

Referring to FIG. 6, a wireless sensor network stack includes a physical layer Ll, a media access control (MAC) layer L2, an adaptation layer L3 and an IPv6 layer L4. A transmission control protocol (TCP), a user datagram protocol (UDP) and an Internet control message protocol (ICMP) are positioned on the IPv6 layer L4, and an application layer is positioned on the TCP, UDP and ICMP.

The physical layer Ll and the MAC layer L2 are standardized in accordance with IEEE 802.15.4-2003, the adaptation layer L3 is standardized in accordance with IETF Internet draft (montenegro-lowpan-ipv6-over-802.15.4), and the IPv6 layer L4 is standardized in accordance with RFC 2460 and related specifications.

An IPv6 head format that is adapted to the present invention will be described with reference to FIG. 7. FIG. 7 is a figure of a header format of IPv6. FIG. 8 shows an example of a MAC/PHY layer data frame format as shown in FIG. 6.

Referring to FIG. 7, a header format of an IPv6 may have a size of 40 octets as defined by 10 columns x 32 bits, and may include a version, a priority, a flow level, a payload length, the next header, a hop limitation, a 128-bit source address and a 128-bit destination address.

Moreover, a frame according to the IEEE 802.15.4-2003 standard includes a beacon frame for transmitting a beacon by a coordinator, a data frame for transmitting data, a response frame for informing when the data frame is received and a MAC command frame.

Referring to FIG. 8, a data frame of a MAC/PHY layer includes a packet format of a physical layer and a packet format of a MAC layer.

A packet format of the physical layer includes a preamble sequence, a start-of-frame delimiter (SFD), a frame length and a MAC protocol data unit (MPDU).

A packet format of the MAC layer includes a frame control, a sequence number, an addressing field, a data payload and a frame check sequence (FCS).

Each device of a wireless sensor network adapted to the present invention may be represented as a node of a tree having a multi-hop, as shown in FIG. 9. FIG. 9 is a schematic diagram illustrating a multi-hop tree according to the present invention. For ease of description, the same reference numerals will be used to refer to the same or like parts in the structure of a wireless sensor network as illustrated in FIG. 5.

Referring to FIG. 9, in a tree structure, a node 'A' corresponding to a root represents a PAN coordinator, and a depth of the node 'A' is O'. Nodes 'B', 'D' and 'F' each represent a router, and nodes 'C, 'E', 'G', 'H' and T each represent a terminal device.

The nodes are communication devices which have mobile communication functions and use low power. The nodes may be a source node generating data, a destination node receiving the data, or an intermediate node disposed between the source node and the destination node to relay the data. Moreover, each of the nodes may be connected to another node in a hierarchical structure. FIG. 10 is a block diagram illustrating a sensor node performing a method for setting a hierarchical routing path according to the present invention.

Referring to FIG. 10, a sensor node that performs a hierarchical routing path setting method according to the present invention includes a logical processing part 100, a hardware processing part 200 and an antenna 300. The logical processing part 100 includes an application module 110, a sensing processing module 120, an Internet Protocol (IP) processing module 130, an adaptation layer packet processing module 140, a routing processing module 150, a neighbor node information managing module 160, and a MAC layer module 170. In this exemplary embodiment, elements of the logical processing part 100 are separately described in logical terms for ease of understanding regardless of whether or not they are separate physical hardware elements.

The hardware processing part 200 includes a sensing device 210 observing an environment, a central processing unit (CPU) 220, a memory 230, a network device 240 performing communication, and a flash memory 250 storing data for a long time.

Conventionally, in a wireless sensor network, for example, a ZigBee network, information for managing and maintaining a network by each node is stored in a table type. The information stored in the table names with a network information base (NWK IB). The NWK IB may be stored in the memory. The NWK IB includes the maximum number of children, the maximum depth of a network tree, the maximum number of ZigBee routers that may be used as children, information related to a broadcast transmission, a neighbor table which has information of a neighbor node, a path table, security-related information and so on. Information such as a PAN identifier, a 16-bit address of a parent or a child of oneself, a 16-bit network address, a device type, a relationship between oneself and a neighbor node and so on is stored in the neighbor table.

Moreover, information such as a status of an activation period of a neighbor node, 64-bit addresses of all neighbor, a beacon order, an authority that is able to approve network participation requests, a transmission failure ratio, a latent parent, a link quality indicator, a logical channel value, a beacon frame arrival time, a beacon transmission time offset, etc., may be optionally stored in the neighbor table. Information, which is used for searching for a path in order to transmit data from a multi-hop network to a destination, is stored in the path table.

The memory 230 stores a neighbor node address. The neighbor node information may be provided through a MAC layer module 170. A service of the MAC layer module 170 includes beaconing. The neighbor node information is used for a routing processing module process in order to search for a short path.

The sensing device 210 may include a temperature sensor, a moisture sensor, an illumination sensor, an ultraviolet ray sensor, etc.

The network device 240 may perform bidirectional communication with another node having a predetermined identification. For example, Bluetooth, IEEE 802.15.4, ZigBee, etc., are mounted to the network device 240.

Packet information arrived at the network device 240 is processed through the MAC layer module 170, and then provided to the adaptive layer packet processing module 140. The adaptive layer packet processing module 140 may perform a packet processing process. The packet processing process may include header parsing, packet fragmentation (separation/reassembling), header compression, etc.

A packet arrived at the adaptive layer packet processing module 140 is provided to the application module 110 via the IP processing module 130. The IP processing module 130 perform a routing process when the packet will be routed.

The sensor node may be operated as a source node which is a packet is transmitted, the next hop node (or a relay node) which transmits the packet, or a destination node which receives the packet.

During a routing operation, each of the source node and a destination node numbers one, respectively, and the next hop node numbers one or more than one. When the source node and the destination node are closely disposed to each other, the next hop node may be omitted. When the sensor node is a source node, the sensor node searches for a plurality of first neighbor nodes as a routing transmitting a packet is started. The searching process, the sensor node transmits the packet to an adjacent node closely adjacent to the destination node of the first neighbor nodes, when a destination node is not included in the first neighbor nodes. Here, the sensor node transmits the packet to the destination node, when the destination node is included in the searched neighbor nodes.

When the sensor node is the next hop node, the sensor node searches for a plurality of second neighbor nodes in accordance with a packet is received from the source nodes, and then transmits the packet to the destination node or an adjacent node closely adjacent to the destination node.

Therefore, a hop count for the packet transmission is smaller than the hop count for hierarchically connecting to the source node and the destination node.

FIG. 11 is a schematic diagram illustrating a method for assigning an address according to an exemplary embodiment of the present invention. Particularly, under a condition of MC=3, an address assignment will be described.

Referring to FIG. 11, a node T is positioned at the top layer, and the node T is connected to a node '2', a node '3' and a node '4' as a child node. Thus, the nodes '2', '3' and '4' are connected to the node ' 1 ' as a parent node. The child node represents a node that is connected to a lower layer node of the corresponding node with respect to a predetermined node in a hierarchical structure. The parent node, in contrast with the child node, represents a node that is connected to a higher layer node of the corresponding node with respect to a predetermined node. Here, the connection represents a logical connection or a wireless connection may include a physical connection, a wireless connection without a physical connection, or a wire connection.

The node '2' is connected to a node '5', a node '6' and a node '7' as a child node, and the node '5' is connected to a node ' 14', a node ' 15' and a node ' 16' as a child node. Thus, the nodes '5', '6' and '7' are connected to the node

'2' as a parent node, and the nodes ' 14', ' 15', and ' 16' are connected to the node

'5' as a parent node.

The node '6' is connected to a node ' 17', a node ' 18' and a node ' 19' as a child node. Thus, the nodes ' 17', 18', and ' 19' are connected to the node '6' as a parent node.

A node which will be assigned an address determines whether its own child exists or not to assign an address according to the following Equation 1 when the child does not exist. In this embodiment, it is assumed that all nodes know their own depth. Equation 1

FC-MC* AP+ 1

Here, 'FC represents a child node address, 'MC represents the maximum number of children, and 'AP' represents a parent node address. When a parent node has no child, a new child is to be a first child so that the parent node receives a new short address through Equation 1.

When a new child node is not a first child node of a parent node, an IEEE 802.15.4 device receives an address, which is the highest address of a child corresponding to a parent node to which 1 has been added. For address assignments, the router maintains a neighbor table storing the address information of children and parents.

When a child node exists, an IEEE 802.15.4 device assigns an address, which is the highest address of a child node to which 1 has been added.

In a routing path setting method according to a first embodiment of the present invention, a path for routing a packet will be calculated as follows.

A current node address, a depth of a current node and a destination node address are defined as 'C, 'DC, 'D', respectively. An ancestor positioned at a depth 'D' of a node 'K' are defined as 'AA(D, K)'. Here, a current node is a node through which a packet flows during a routing process. When the current node is included in an ancestor group of a destination node, the next hop node address (or the next transmitting node) is 'AA(DC+ 1, D)'. When the current node is included in a descendant group of a destination node, the next hop node address is 'AA(DC-I, C)'. In another case, the next hop node address is 'AA(DC-I, C)'. Here, the descendant node denotes a plurality of nodes connected to an upper layer thereof with respect to one of nodes (i.e., a predetermined node) in a hierarchical structure, and includes the above-mentioned parent node. The child node, in contrast with the descendant node, denotes a node that is connected to a lower layer node of the corresponding node with respect to a predetermined node in a hierarchical structure. An example of a method for transferring a packet according to a first exemplary embodiment of the present invention will be described with reference to a following FIG. 11.

FIG. 12 is a schematic diagram illustrating a method for setting a routing path using an address assigning method of FIG. 11. For example, when a source node is a node ' 14' and a destination node is a node ' 19', a method for setting a routing path will be described.

Referring to FIG. 12, a parent node of the node ' 14' is a node '5'. Here, a node '5' is a current node. However, the node '5' that is a current node is not included in an ancestor group of a node ' 19' that is a destination node, and is not included in a descendant group. Therefore, the next hop node address is a parent node of a node '2'. Here, the node '2' is a current node.

A node '2' that is a current node is included in an ancestor group of a destination node. Thus, an address candidate of the next hop node is a node '6' or a node '7'. However, a node '7' is not included into an ancestor group of a destination node, so that the next hop node address is a node '6'. Here, the node

'6' is a current node.

A node '6' that is a current node is included in an ancestor group of a destination node. Thus, an address candidate of the next hop node is a node ' 17', a node ' 18' and a node ' 19'. However, a destination node is included in the address candidate, so that a routing process is ended. According to the set routing path, a node '5', a node '2' and a node '6' as a relay node are disposed between a node ' 14' that is a source node and a node ' 14' that is a destination node, so that a packet transmitted from the node ' 14' is transmitted to a node ' 19' through a node '5', a node '2', a node '6'.

In the first embodiment of the present invention, a packet is transmitted to the next hop node (i.e., a parent node or a child node) of a path from a source node to a destination node. A packet is always transmitted via the next hop node, so that a routing time is long and the packet traffic is increased. FIGS. 13 and 14 are schematic diagrams illustrating a method for setting a routing path according to another exemplary embodiment of the present invention. For ease of description, it is assumed that a topology of a multi-hop tree as shown in FIGS. 13 and 14 is identical to that of a multi-hop tree as shown in FIG. 11. The routing path setting method may be adapted in a wireless sensor network, for example, a LoWPAN.

Referring to FIG. 13, a node ' 14' that is a source node searches for the nearest node adjacent to a node ' 19' that is a destination node of its own neighbor nodes. In this embodiment, a neighbor node of a source node is a node '2', a node '5', a node ' 15' and a node ' 16'. The node '2' that has the shortest hop distance between the destination node and the nodes '2', '5', ' 15' and ' 16' is selected as the next hop node.

Then, as shown in FIG. 14, the node '2' where a packet arrives searches for the nearest node adjacent to a node ' 19' that is a destination node of its own neighbor nodes. In this embodiment, neighbor nodes of the node '2' is a node T, a node '5', a node '6', a node ' 17', a node ' 18' and a node ' 19'. Here, the node ' 19' that is a destination node is included in the neighbor nodes, so that the node '2' transmits the arrived packet to the node ' 19'.

As a result, in the same topology, when a method of setting a routing path according to the second embodiment is compared to a method of setting a routing path according to the first embodiment, the total hop distance is decreased from four hops to two hops.

FIG. 15 is a flowchart illustrating a method for setting a hierarchical routing path according to another exemplary embodiment of the present invention.

Referring to FIG. 15, as a hierarchical routing operation is started, a source node, a destination node and the next hop node that is nearest to the source node and the destination node are set (step S 105).

Then, a first hop distance in a hierarchical routing path from the source node to the destination node and a second hop distance in a hierarchical routing path from the nearest next hop node to the destination node are calculated (step SI lO).

Then, the next hop node in a hierarchical routing path is set (step Sl 15).

Then, a neighbor table is queried (step S 120), and neighbor node information is extracted from the neighbor table (step S 125).

Then, a third hop distance is calculated in a hierarchical routing path from the neighbor node to the destination node (step S 130).

Then, the first hop distance and the third hop distance are compared with each other (step S 135). Then, when the first hop distance is less than or equal to the third hop distance, it is checked whether the whole search for the neighbor table has ended or not (step S 140). When the whole search for the neighbor table has not ended in step S 140, the process feeds back to step S 120. When the whole search for the neighbor table has ended in step S 140, a packet is transmitted to the next hop node (step S 145), and then the hierarchical routing operation has ended.

In step S 135, when the first hop distance is greater than the third hop distance, the second hop distance and the third hop distance are compared with each other (step S 150).

When the second hop distance is greater than the third hop distance, the queried neighbor node is set to be the next hop node (step S 155), and then the process feeds back to step S 140.

This invention has been described with reference to the example embodiments. It is evident, however, that many alternative modifications and variations will be apparent to those having skill in the art in light of the foregoing description. Accordingly, the present invention embraces all such alternative modifications and variations as fall within the spirit and scope of the appended claims.

Industrial Applicability

According to the present invention, a hierarchical routing operation may be performed using a 16-bit short address that is dynamically assigned in a wireless sensor network, for example, a low-power wireless personal area network (LoWPAN) based on Internet Protocol version 6 (IPv6) (6LoWPAN). Particularly, in a wireless sensor network, hierarchical routing is performed by using neighbor node information, and the nearest node adjacent to a destination node receiving a packet is searched for to transmit the packet, so that a hop count according to a packet transmission may be decreased. Moreover, the total hop count may be decreased, so that a routing operation may be fast and traffic generated between the nodes may be decreased.

Claims

1. A method for setting a routing path in a wireless sensor network transferring a packet between a source node and a destination node, the method comprising:

(a) searching for a neighbor node of the source node as the routing is started;

(b) transferring a packet to the destination node when the destination node is included in the neighbor nodes, and finishing the routing; (c) searching for the nearest node to the destination node of the neighbor nodes, when the destination node is not included in the neighbor nodes, to transmit a packet to the nearest node; and

(d) searching for neighbor nodes, which is performed by the nearest node, to feedback to step (b).

2. The method of claim 1, wherein a hop count for the packet transfer is less than a hop count for hierarchically connecting to the source node and the destination node.

3. The method of claim 1, wherein the neighbor nodes is obtained from a neighbor table of the source node.

4. A method for setting a routing path in a wireless sensor network, the method comprising: (a) setting a current node, a destination node and the next hop node that is nearest to the current node and the destination node;

(b) calculating a first hop distance in a hierarchical routing path from the current node to the destination node and a second hop distance in a hierarchical path from the next hop node nearest to the destination node; (c) setting the next hop node in a hierarchical routing path;

(d) querying a neighbor table to extract neighbor node information from the neighbor table;

(e) calculating a third hop distance in a hierarchical routing path from the neighbor node to the destination node;

(f) comparing the first hop distance with the third hop distance;

(g) checking whether or not the whole search for a neighbor table has ended, when the first hop distance is less than or equal to the third hop distance;

(h) feeding back to step (d) when the whole search for a neighbor table has not ended, and transferring a packet to the next hop node when the whole search for a neighbor table has ended;

(i) comparing the second hop distance with the third hop distance when the first hop distance is greater than the third hop distance; and

(j) setting the searched neighbor node as the next hop node to feedback to step (g), when the second hop distance is greater than the third hop distance.

5. An apparatus for setting a routing path in a wireless sensor network, the apparatus comprising: a destination node finally receiving a packet; a source node searching for a plurality of first neighbor nodes as a routing for transmitting a packet is started and transmitting a packet to the nearest node of the destination node of the first neighbor nodes when the destination node is not included in the first neighbor nodes; and the next hop node searching for a plurality of second neighbor nodes as a packet is received from the source node and transmitting the packet to the destination node or the nearest node of the destination node of the second neighbor nodes.

6. The apparatus of claim 5, wherein the source node transmits a packet to the destination node when a destination node is not included in the neighbor nodes.

7. The apparatus of claim 5, wherein each of the destination node and the source node numbers one.

8. The apparatus of claim 5, wherein the next hop distance is no more than one.

9. The apparatus of claim 5, wherein a hop count for the packet transfer is less than a hop count for hierarchically connecting to the source node and the destination node.

10. The apparatus of claim 5, wherein the neighbor nodes is obtained from a neighbor table of the source node.

11. An apparatus for setting a routing path in a wireless sensor network, the apparatus comprising: a logical processing part including a sensing device and a memory; a hardware processing part including a neighbor node information managing module that manages a neighbor node using a neighbor table stored in the memory; and an antenna wirelessly connecting to an external node and the hardware processing part, wherein the logical processing part and the hardware processing part finally receive a packet from the external node in a destination node operation, and search for a first neighbor nodes in a source node operation, to transmit the packet to the nearest node of the destination node of the first neighbor node when the destination node is not included in the first neighbor node.

12. The apparatus of claim 11, wherein the logical processing part and the hardware processing part search for a plurality of second neighbor nodes based on a packet from the source node when the next hop node is operated, and transmit the packet to the destination node or the nearest node of the destination node of the second neighbor nodes.