According to an embodiment, a first device includes: a first transceiver configured to transmit two or more first carrier signals using an output of a first reference signal source and to receive two or more second carrier signals; and a calculation unit, and a second device includes: a second transceiver configured to transmit the two or more second carrier signals using an output of a second reference signal source that operates independently of the first reference signal source and to receive the two or more first carrier signals. A frequency group of the two or more first carrier signals and a frequency group of the two or more second carrier signals are identical or substantially identical to each other, and the calculation unit calculates the distance between the first device and the second device based on a phase detection result obtained by receiving the first and second carrier signals.