To avoid communication disruption resulting from misalignment of transmission and reception timing by correcting the misalignment of transmission and reception timing with a communication partner.
A slave unit 200 includes: a piezoelectric element section 226 for detecting or generating a ultrasound; a communication section 218 for performing communication using the ultrasound; a memory section 202 for storing a common table which is shared with a master unit 100 and in which a slot with a certain length of time are chronologically allocated; a slot timing control section 208 for performing synchronization with the master unit 100 and giving a transmission or reception instruction based on the slot; a distance acquisition section 212 for acquiring distance information in relation to a distance to the master unit 100; a time measurement section 214 for measuring time required for the communication section 218 to receive a signal transmitted from the master unit 100 based on the table; and a slot timing correction instruction section 210 for calculating a time lag in relation to the synchronization with the master unit 100 based on the required time and the distance information to give an instruction to correct misaligned time.
Osamu Suzawa
Kazuhiko Miyasaka