Communication device and communication method

A communication device comprising:

• an ultrasonic oscillating unit which detects or generates an ultrasonic wave;
• a communication unit which transmits and receives information using the ultrasonic wave;
• a storage unit which stores a table including first and second slots to which a first communication command and second communication command to designate communication with a second communication device is respectively allocated in time series, the table being shared by the second communication device;
• and
• a control unit which shifts the communication unit to one of a transmitting state, a receiving state, and a standby state that is neither the transmitting nor the receiving state, synchronously with the second communication device on the basis of the communication command in the table,
• the communication unit transmitting and receiving the information to and from the second communication device, and further using a first packet divided by a time length that does not exceed a predetermined time length and a second packet divided by the time,
• the first packet being included in the first slot,
• the second packet being included in the second slot,
• the first packet including a first slot number that is assigned to the first slot,
• the second packet including a second slot number that is assigned to the second slot.