Vibrational communication system in ultrasonic frequency band

Vibrational communication is a suitable method for exchanging important personal information between information technology devices. Since the vibration propagates only through the vibration medium, the information signal is spatially limited, and it prevents any eavesdropping. However, it has proven slow and unreliable. Therefore, we proposed a vibrational communication method using the ultrasonic band. The characteristics of the vibration propagation were measured using piezoelectric elements as the transmitter and receiver and plastic toy blocks as a vibration medium. We performed a successful demonstration of the vibrational communication using a time period per bit of 2 ms, achieving a bit rate of 500 bps. To eliminate unpleasant noise and vibration sensations, a micro-electro-mechanical system (MEMS) resonant device using a higher frequency band was designed and used to simulate its frequency characteristics. Subsequently, the MEMS device was fabricated and a vibrational communication using the MEMS device successfully achieved a bit rate of 4 kbps.