Abstract: Provided is a method of constructing a tree network which includes a first node. The method comprises: (a) the first node determining if there is a child node and requesting a parent node to allow the first node to withdraw if there is no child node; (b) selecting a child node based on remaining amounts of battery power of each child node if there are child nodes of the first node; (c) exchanging positions of the first node and the selected child node and requesting the parent node to allow the first node to withdraw if the child node selected in operation (b) does not have child nodes; and (d) repeating operations (b) and (c) if the child node selected in operation (b) has child nodes. The present invention solves the problem of decreasing lifetimes of upper nodes that consume more battery power than lower nodes due to more traffic transmission and reception.

Abstract: Provided is a method for managing dormant nodes in a wireless sensor network. The method includes the steps of: a) acquiring and storing information on distance and location of sensor nodes registered in a corresponding cluster among at least one cluster managed by a managing node; b) selecting a dormant object node among the sensor nodes by the managing node; c) transmitting dormant information that the dormant object node should go into a dormant state for a predetermined period through a beacon message to the dormant object node and creating a dormant node management table; and d) updating a dormant time of the dormant node management table every beacon cycle by the managing node according to setup of a dormant time central managing function and notifying dormancy expiration to the corresponding dormant node.

Abstract: An apparatus for analyzing a USN protocol includes a packet analyzer and a protocol analyzer. The packet analyzer collects packets communicated between USN sensor nodes through at least one or more channels. The protocol analyzer processes/displays the collected packets using an XML schema defined according to the USN protocol. Thus, the USN protocol analyzing apparatus can decode/encode packets collected through a plurality of channels.

Abstract: Provided is an apparatus and method for controlling multi-channel access in USN-based MAC. The multi-channel access control apparatus includes a channel scanner, a control channel preoccupier, and an available channel exchanger. The channel scanner scans at least one or more available channels among the N data channels in a Tx sensor node. The control channel preoccupier preoccupies, in the Tx sensor node, the control channel through control channel sensing and back-off and broadcasts a preamble on the control channel periodically. The available channel exchanger detects, in an Rx sensor node, the available channels available to the Tx sensor node on the basis of the received preamble, selects a channel available to the Rx sensor node among the detected available channels, and transmits information about the selected channel to the Tx sensor node.

Abstract: Provided are a method and apparatus for controlling media access in a sensor network and a method of managing traffic information. Since traffic information is exchanged between nodes and data is transmitted by using a dynamic long preamble according to receiver nodes, data transmission efficiency can be improved, energy consumed to transmit the long preamble can be reduced, and data transmission delay can be reduced as well.

Abstract: Provided is a method of transmitting/receiving data in a sensor node for reducing overhearing of sensor nodes, and a sensor network which implements the method. A sender node having transmission data from among a plurality of nodes which perform a low power listening (LPL) operation in an asynchronous manner at predetermined time intervals, generates a long preamble including short preambles, each having information including a destination address of the transmission data, a remainder of the long preamble, and a length of the transmission data, and sequentially transmits the second preamble and the transmission data. A receiver node from among the plurality of nodes determines whether a valid signal is sensed during an active state in the LPL operation. If it is determined that the valid signal is sensed, the receiver node receives the short preamble transmitted from the sender node.

Abstract: A Ubiquitous Sensor Network (USN) system using multi-channel having differential radio power and a method of configuring the USN system are provided. The USN system and the method include a sink node performing a communication with a sensor node using at least one or more frequency signal having differential outputs; and a sensor node performing the communication with the sink node using the at least one or more frequency signal. The USN system and the method simultaneously use a control frequency signal having a high output power and a data frequency signal having an output power lower than that of the control frequency signal, thereby reducing a beacon transmission delay, enabling time synchronization between the sensor nodes, and preventing collisions between beacons due to beacon relays among the sensor nodes, so as to configure a more efficient sensor field.

Abstract: Provided is a method for buffering a receive packet in a sensor node including a radio frequency (RF) transceiver, a media access control (MAC) hardware block and a micro controller unit (MCU).

Abstract: Provided is a distributional alert system using a ubiquitous sensor network (USN). When a disaster occurs, the distributional alert system detects it in a sensor node, informs the area where the disaster occurs of danger through an actuator, such as siren, or informs a management system of the danger through a wired/wireless network. The distributional alert system includes: a first sensor node for generating sense data by sensing surroundings with a sensor therein, determining whether a disaster occurs by analyzing the sense data, and creating and transmitting emergency data based on the determination result, while forming a sensor network; and an alerting node for receiving emergency data from the first sensor node on the sensor network, and outputting disaster circumstantial information to a sensor field of the sensor network upon receipt of the emergency data.

Abstract: A method for selecting an access point by considering state information including the number of mobile stations connected in each access point and a traffic amount at each access point is disclosed. The method includes the steps of a) at access points, inserting a first state information of the access point about the number of connected mobile stations into a Beacon frame/Probe Response message frame; b) at the access points, the Beacon frame/Probe Response message frame of the first state information is transmitted to the mobile station; c) at the access points, inserting a second state information about a traffic amount into the Beacon frame/Probe Response message frame; d) at each the access points, the Beacon frame/Probe Response message frame of the second state information is transmitted to the mobile station; and e) at the mobile station, selecting one of access points based on the first and second state information.

Abstract: A billing method and system connected to a wireless access point for wireless network access for charging for a service provided to a user terminal connected to the network. The wireless access point connects the user terminal to a wireless network. The wireless access point uses a hardware address of an access-authenticated user terminal to measure a data packet usage amount transmitted to the user terminal. The system bills each user according to the packet usage amount based on the data packet usage amount measured by the wireless access point.

Abstract: An apparatus is provided for use with a mobile air blower which allows the blower air stream to be oscillated vertically or redirected away from the work piece to avoid damage to vehicles and structure that are in the path of the air blower air stream and the apparatus provides for redirection of the air stream in forward and rearward directions.