Communication terminal and communication method

A communication terminal which is included in an ad-hoc network and which relays a data packet between a transmission terminal and a reception terminal,

• the transmission terminal selecting, as route candidates, a plurality of routes that lead to the reception terminal in a descending order of broadness of bandwidth or in an ascending order of delay time,
• the communication terminal comprising:
• a communication section that communicates the data packet;
• and
• a control section, which judges, at predetermined time intervals during the communication of the data packet, whether or not the communication terminal is positioned at a branching point of two or more routes among the selected plurality of route candidates based on a control packet unicasted to the plurality of route candidates, and which selects, when the communication terminal is positioned at the branching point of two or more routes among the selected plurality of route candidates and when a bandwidth used for the communication of the data packet has become equal to or less than a predetermined value, the route that has the broadest communication bandwidth or the smallest delay time among other route candidates that go through the branching point, and which switches the route used for the communication of the data packet.

A communication method conducted by a communication terminal included in an ad-hoc network, the communication method comprising the steps of:

• communicating a data packet to a reception terminal via at least one relay terminal;
• broadcasting, prior to the communicating of the data packet, a first control packet used for creating routes that lead to the reception terminal;
• selecting, in a descending order of broadness of bandwidth or in an ascending order of delay time and based on a response result of the first control packet, a plurality of routes that lead to the reception terminal as route candidates;
• unicasting, at predetermined time intervals during the communicating of the data packet, a second control packet that is used to confirm, via all or some of the route candidates, a change of a communication state to the reception terminal;
• and
• continuing the communicating of the data packet by selecting, based on a response result of the second control packet which includes information on the bandwidth or the delay time in the route candidates between a communication terminal to the reception terminal, among the route candidates through which the response result of the second control packet has been obtained, that has the broadest communication bandwidth or the smallest delay time, and by switching a route used by the communicating of the data packet to the selected route.

A communication method conducted by a communication terminal which is included in an ad-hoc network and which relays a data packet between a transmission terminal and a reception terminal, the transmission terminal selecting, as route candidates, a plurality of routes that lead to the reception terminal in a descending order of broadness of bandwidth or in an ascending order of delay time, the communication method comprising the steps of:

• communicating the data packet;
• judging, at predetermined time intervals during the communicating of the data packet, whether or not the communication terminal is positioned at a branching point of two or more routes among the selected plurality of route candidates based on a control packet unicasted to the route candidates;
• and
• switching the route used for the communicating of the data packet after selecting, when the communication terminal is positioned at the branching point of two or more routes among the selected plurality of route candidates and when a bandwidth used for the communicating of the data packet has become equal to or less than a predetermined value, the route that has the broadest communication bandwidth or the smallest delay time among other route candidates that go through the branching point.