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 data communication apparatus forms a mesh network together with at least one gateway includes a frame generating unit and a frame transferring unit. The frame generating unit generates a meter data frame to transmit to a gateway. The meter data frame is a frame including meter data. The frame transferring unit transfers the meter data frame received from another data communication apparatus. The meter data frame is addressed to the gateway. The frame generating unit transmits the meter data frame to which number of alternate routing that indicates number of allowable transmission attempts from a data communication apparatus adjacent to a destination gateway of the meter data frame to the gateway is added. The frame transferring unit changes the number of alternate routing added thereto to a value smaller by 1 than a value that has been set and transits the meter data frame to another data communication apparatus.

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 data communication apparatus forms a mesh network together with at least one gateway includes a frame generating unit and a frame transferring unit. The frame generating unit generates a meter data frame to transmit to a gateway. The meter data frame is a frame including meter data. The frame transferring unit transfers the meter data frame received from another data communication apparatus. The meter data frame is addressed to the gateway. The frame generating unit transmits the meter data frame to which number of alternate routing that indicates number of allowable transmission attempts from a data communication apparatus adjacent to a destination gateway of the meter data frame to the gateway is added. The frame transferring unit changes the number of alternate routing added thereto to a value smaller by 1 than a value that has been set and transits the meter data frame to another data communication apparatus.

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 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 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.