Communication Terminal Device, Communication System, and Method of Controlling Communication Terminal Device

1. A communication terminal device comprising: a wireless communication unit configured to wirelessly communicate with control devices; a detection unit configured to detect a control signal instructing start of registration processing for causing a desired control device among the control devices to register the communication terminal device as a target to be controlled; a channel selection unit configured to sequentially select, from a plurality of frequency channels, a frequency channel to be used in transmission of a beacon request for requesting each of the control devices to transmit a beacon signal; a first transmission control unit configured to transmit, via the wireless communication unit, the beacon request to the control devices by using the frequency channel selected by the channel selection unit; and a receiving unit configured to receive, via the wireless communication unit, the beacon signal transmitted from each of the control devices in response to the beacon request, wherein the channel selection unit is configured to select at random a first frequency channel to be used in transmission of the beacon request from the frequency channels, when the detection unit detects the control signal, and the channel selection unit is configured to select at random a first frequency channel to be used in re-transmission of the beacon request, when the detection unit re-detects the control signal.

2. The communication terminal device according to claim 1 , further comprising: a first storage unit configured to store (a) a predetermined parameter included in the beacon signal received by the receiving unit and (b) the frequency channel selected by the channel selection unit in association with each other; and a second transmission control unit configured to transmit a registration request to the desired control device specified by the predetermined parameter by the frequency channel associated with the predetermined parameter, the registration request being for requesting the desired control device to register the communication terminal device as the target to be controlled, wherein the receiving unit is configured to further receive a registration response signal transmitted from the desired control device in response to the registration request, the registration response signal indicating that the desired control device has completed the registration of the communication terminal device or that the desired control device rejects the registration.

3. The communication terminal device according to claim 2 , further comprising a sensor unit configured to detect a receiving electrical field intensity of the beacon signal received by the receiving unit, wherein the first storage unit is configured to, for each of the control devices, store the receiving electrical field intensity detected by the sensor unit in addition to the predetermined parameter and the frequency channel in association with one another, and the second transmission control unit is configured to transmit the registration request to the desired control device specified by the predetermined parameter in a group including a highest receiving electrical field intensity among at least one group in which the predetermined parameter, the frequency channel, and the receiving electrical field intensity are associated with one another in the first storage unit.

4. The communication terminal device according to claim 1 , further comprising a transmission power control unit configured to lower a transmission power level from a predetermined transmission power level, when the first transmission control unit is to transmit the beacon request.

5. The communication terminal device according to claim 4 , wherein the transmission power control unit is configured to, when the first transmission control unit completes the transmission of the beacon request, set the transmission power level lowered for the transmission of the beacon request back to the predetermined transmission power level.

6. The communication terminal device according to claim 1 , wherein the communication terminal device is one of a home appliance and an energy-related device each of which has a communication function.

7. The communication terminal device according to claim 1 , wherein the beacon signal is a beacon frame compliant with IEEE802.15.4 standard, and the beacon request is a beacon request frame compliant with the IEEE802.15.4 standard.

8. The communication terminal device according to claim 1 , wherein the beacon signal is a probe response frame compliant with IEEE802.11 standard, and the beacon request is a probe request frame compliant with the IEEE802.11 standard.

9. A communication system comprising: the communication terminal device according to claim 1 ; and a control device that transmits the beacon signal in response to the beacon request transmitted from the communication terminal device, and registers the communication terminal device as the target to be controlled in response to the registration request transmitted from the communication terminal device.

10. A communication terminal device comprising: a wireless communication unit configured to wirelessly communicate with control devices; a detection unit configured to detect a control signal instructing start of registration processing for causing a desired control device among the control devices to register the communication terminal device as a target to be controlled; a channel selection unit configured to sequentially select, from a plurality of frequency channels, a frequency channel to be used in transmission of a beacon request for requesting each of the control devices to transmit a beacon signal; a first transmission control unit configured to transmit, via the wireless communication unit, the beacon request to the control devices by using the frequency channel selected by the channel selection unit; a receiving unit configured to receive, via the wireless communication unit, the beacon signal transmitted from each of the control devices in response to the beacon request; and a second storage unit configured to store information indicating a frequency channel that is currently used to transmit the beacon request, wherein the channel selection unit is configured to select at random a first frequency channel to be used in transmission of the beacon request from the frequency channels, when the detection unit detects the control signal, and the channel selection unit is configured to, when the detection unit re-detects the control signal, determine, as a first frequency channel to be used in re-transmission of the beacon request, one of (a) the frequency channel stored in the second storage unit and (b) a subsequent frequency channel.

11. A control method of controlling a communication terminal device, the method comprising: detecting a control signal instructing start of registration processing for causing a desired control device among a plurality of control devices to register a communication terminal device as a target to be controlled; sequentially selecting, from a plurality of frequency channels, a frequency channel to be used in transmission of a beacon request for requesting each of the control devices to transmit a beacon signal; transmitting the beacon request to each of the control devices by using the frequency channel selected in the selecting; and receiving the beacon signal from each of the control devices in response to the beacon request, wherein in the selecting, a first frequency channel to be used in transmission of the beacon request is selected at random from the frequency channels, when the control signal is detected in the detecting, and in the selecting, a first frequency channel to be used in re-transmission of the beacon request is selected at random, when the control signal is re-detected in the detecting.