Abstract: A node includes a time difference measurement unit and a time setting unit. The time difference measurement unit measures a time difference between a first time based on latest received time information and a second time based on second-latest received time information. The time setting unit calculates an adjustment time difference when the time difference exceeds an allowable range of error that is smaller than an allowable range of maintainable communication, sets a time obtained by adding the adjustment time difference and the second time to the time of the node when the adjustment time difference is within the allowable range of maintainable communication, and sets a time obtained by adding a time difference corresponding to the allowable range of maintainable communication and the second time to the time of the node when the adjustment time difference exceeds the allowable range of maintainable communication.

Abstract: An ad hoc network system includes a plurality of nodes that communicate with a specific node. Each of the nodes includes a calculator and a selector. The calculator calculates a cumulative value of the number of communication nodes connected through the node by adding the numbers of communication nodes from an upstream side, which is a side closer to the specific node than the node, to the node. The selector selects a node serving as a connection destination out of the nodes located on the upstream side on the basis of the cumulative value of the number of communication nodes calculated by the calculator.

Abstract: A communication system includes: a specific node; and a plurality of nodes that are installed at fixed positions and perform ad hoc wireless communication with the specific node. The nodes each include a link quality evaluating unit, an upstream route constructing unit, a communicating unit, and a downstream route constructing unit. The link quality evaluating unit performs route evaluation using a hello frame based only on a track record of reception of the hello frame in order to perform upstream communication toward the specific node to form a network. The upstream route constructing unit constructs an upstream route based on the route evaluation. The communicating unit performs upstream communication toward the specific node on a regular basis with a predetermined frequency. The downstream route constructing unit constructs a downstream route from the specific node based on a route in the upstream communication toward the specific node.

Abstract: The present invention increases accommodation efficiency in a wireless master station for wireless slave stations, and efficiently uses wireless resources while controlling traffic. In a communication system in which a plurality of wireless slave stations 2-1, 2-2, 2-3, . . . , perform wireless communication with wireless master stations 1-1 and 1-2 directly or through another wireless slave station and which performs communication from the wireless master stations with a collection control device 3 by means of wired communication or the like. The collection control device 3 stores first through fourth threshold values a, b, c, and d in memory, and makes efficient use while suppressing traffic by performing a “connection suppression notification”, a “specific high-frequency communication stop notification”, and an “accommodation refusal notification”, and performs functionality control through stages according to the number of accommodated wireless slave stations.

Abstract: A software update system includes an administration server, a wireless communication terminal, and a wireless-communication key station. The wireless communication terminal is configured to be connected to the administration server through a communication network. The a wireless-communication key station is configured to be positioned between the administration server and the wireless communication terminal, and to perform processing of distributing software of an update object transmitted from the administration server to the wireless communication terminal.

Abstract: The present invention increases accommodation efficiency in a wireless master station for wireless slave stations, and efficiently uses wireless resources while controlling traffic. In a communication system in which a plurality of wireless slave stations 2-1, 2-2, 2-3, . . . , perform wireless communication with wireless master stations 1-1 and 1-2 directly or through another wireless slave station and which performs communication from the wireless master stations with a collection control device 3 by means of wired communication or the like. The collection control device 3 stores first through fourth threshold values a, b, c, and d in memory, and makes efficient use while suppressing traffic by performing a “connection suppression notification”, a “specific high-frequency communication stop notification”, and an “accommodation refusal notification”, and performs functionality control through stages according to the number of accommodated wireless slave stations.

Abstract: A software update system includes an administration server, a wireless communication terminal, and a wireless-communication key station. The wireless communication terminal is configured to be connected to the administration server through a communication network. The a wireless-communication key station is configured to be positioned between the administration server and the wireless communication terminal, and to perform processing of distributing software of an update object transmitted from the administration server to the wireless communication terminal.

Abstract: An ad hoc network system includes a plurality of nodes that communicate with a specific node. Each of the nodes includes a calculator and a selector. The calculator calculates a cumulative value of the number of communication nodes connected through the node by adding the numbers of communication nodes from an upstream side, which is a side closer to the specific node than the node, to the node. The selector selects a node serving as a connection destination out of the nodes located on the upstream side on the basis of the cumulative value of the number of communication nodes calculated by the calculator.

Abstract: A mobile terminal being a searching source that searches for a communication device transmits a searching request addressed to a communication device being a searching destination using a plurality of channels without waiting for a reply to the searching request. A communication device adjacent to the mobile terminal being the searching source, upon receiving a reply to the searching request transmitted by the transmitting from the searching destination, holds the received reply. The mobile terminal being the searching source transmits an inquiry to the adjacent communication device using a plurality of channels about whether a reply to the transmitted searching request has been received from the searching destination. With this configuration, in an ad hoc network with a reactive scheme, the time taken for searching related to a partner device can be shortened.

Abstract: A communication system includes: a specific node; and a plurality of nodes that are installed at fixed positions and perform ad hoc wireless communication with the specific node. The nodes each include a link quality evaluating unit, an upstream route constructing unit, a communicating unit, and a downstream route constructing unit. The link quality evaluating unit performs route evaluation using a hello frame based only on a track record of reception of the hello frame in order to perform upstream communication toward the specific node to form a network. The upstream route constructing unit constructs an upstream route based on the route evaluation. The communicating unit performs upstream communication toward the specific node on a regular basis with a predetermined frequency. The downstream route constructing unit constructs a downstream route from the specific node based on a route in the upstream communication toward the specific node.

Abstract: A terminal used in a network that constructs a communication route with ad hoc communications is connected to a server via a gateway. The terminal generates downstream route information from the server to a specific terminal based on information relating to occurrence of downstream communication from the server to the specific terminal, the information being included in a header of upstream communication from the specific terminal to the server, and preferentially retains the downstream route information.

Abstract: A node includes a time difference measurement unit and a time setting unit. The time difference measurement unit measures a time difference between a first time based on latest received time information and a second time based on second-latest received time information. The time setting unit calculates an adjustment time difference when the time difference exceeds an allowable range of error that is smaller than an allowable range of maintainable communication, sets a time obtained by adding the adjustment time difference and the second time to the time of the node when the adjustment time difference is within the allowable range of maintainable communication, and sets a time obtained by adding a time difference corresponding to the allowable range of maintainable communication and the second time to the time of the node when the adjustment time difference exceeds the allowable range of maintainable communication.

Abstract: A GPS receiver displays information concerning a distance to a destination and a direction with respect to the destination and the like. The information is provided according to a preset operating condition on the basis of data which include position data of the destination which is set in advance and position data of the current position which is obtained from radio waves emitted from GPS satellites orbiting the earth. The GPS receiver includes a memory which stores data of operating conditions corresponding to first, second, third and fourth operation modes. The parameters of the operating conditions of the four operation modes are different from each other in at least a part thereof.