Abstract: A control device includes: a receiving unit that receives a first beacon request for performing registration processing from a communication terminal device; a detection unit that detects a control signal indicating a request for starting the registration processing; a registration control unit that starts the registration processing when the detection unit detects the control signal and executes the registration processing for a certain period; and a transmission control unit that: transmits the beacon signal when the receiving unit receives the first beacon request in a period during which the registration control unit is executing the registration processing; and avoids transmitting the beacon signal when the first beacon request is received in a period during which the registration control unit is not executing the registration processing.

Abstract: A communication device according to the present invention aims to restart data transmission/reception between communication devices in a short amount of time, without performing key sharing again, even when a communication device of a transmitting side is rebooted. The communication device includes a volatile memory storing a count value, a generator generating data including a count value, a communicator transmitting data to another communication device, a storage instructor, each time the communicator transmits data, updating the volatile memory with a count value, and a nonvolatile memory. A count value is incremented each time the communicator transmits data, the storage instructor causes the nonvolatile memory to store a count value at certain intervals, and the generator, when the communication device is rebooted, includes in data a sum of a certain value and a count value stored in the nonvolatile memory.

Abstract: A communication terminal device includes the following units. A detection unit detects a control signal instructing start of registration processing. A channel selection unit selects at random, from a plurality of frequency channels, the first frequency channel to be used in transmission of a beacon request when the control signal is detected. A scan control unit transmits the beacon request to the control devices by using the selected frequency channel. A receiving unit receives the beacon signal transmitted from each of the control devices. A list storage unit stores a predetermined parameter included in the beacon signal and the frequency channel in association with each other. A registration control unit transmits a registration request signal to the control device.

Abstract: A communication device according to the present invention aims to restart data transmission/reception between communication devices in a short amount of time, without performing key sharing again, even when a communication device of a transmitting side is rebooted. The communication device includes a volatile memory storing a count value, a generator generating data including a count value, a communicator transmitting data to another communication device, a storage instructor, each time the communicator transmits data, updating the volatile memory with a count value, and a nonvolatile memory. A count value is incremented each time the communicator transmits data, the storage instructor causes the nonvolatile memory to store a count value at certain intervals, and the generator, when the communication device is rebooted, includes in data a sum of a certain value and a count value stored in the nonvolatile memory.

Abstract: A control device includes: a receiving unit that receives a first beacon request for performing registration processing from a communication terminal device; a detection unit that detects a control signal indicating a request for starting the registration processing; a registration control unit that starts the registration processing when the detection unit detects the control signal and executes the registration processing for a certain period; and a transmission control unit that: transmits the beacon signal when the receiving unit receives the first beacon request in a period during which the registration control unit is executing the registration processing; and avoids transmitting the beacon signal when the first beacon request is received in a period during which the registration control unit is not executing the registration processing.

Abstract: A communication terminal device includes the following units. A detection unit detects a control signal instructing start of registration processing. A channel selection unit selects at random, from a plurality of frequency channels, the first frequency channel to be used in transmission of a beacon request when the control signal is detected. A scan control unit transmits the beacon request to the control devices by using the selected frequency channel. A receiving unit receives the beacon signal transmitted from each of the control devices. A list storage unit stores a predetermined parameter included in the beacon signal and the frequency channel in association with each other. A registration control unit transmits a registration request signal to the control device.