Indoor Airborne Ultrasonic Wireless Communication Using OFDM Methods.

Area of Science:

• Acoustics and Signal Processing
• Wireless Communication Technologies
• Data Security

Background:

• Radio frequency (RF) wireless transmissions raise safety and data security concerns, including signal interception.
• Airborne ultrasound presents a viable alternative for secure indoor wireless communication due to signal confinement.
• Existing RF systems face limitations in secure, short-range data transmission.

Purpose of the Study:

• To implement and evaluate an indoor airborne wireless communication system using ultrasonic transducers.
• To explore the feasibility of using ultrasound for secure data transmission as an alternative to RF.
• To achieve high data rates and extended transmission ranges using ultrasonic signals.

Main Methods:

• Utilized two types of air-coupled capacitive ultrasonic transducers: commercial (50 kHz) and prototype (200-400 kHz).
• Implemented modulation schemes including Binary Phase-Shift Keying (BPSK), Quadrature Phase-Shift Keying (QPSK), and Quadrature Amplitude Modulation (QAM)-based orthogonal frequency division multiplexing.
• Employed a least-squares channel estimation algorithm for phase and amplitude distortion compensation.

Main Results:

• Achieved a maximum data rate of 180 kb/s with 16-QAM over 6 m using commercial transducers.
• Extended transmission range to 11 m (BPSK) and 9 m (QPSK) with data rates of 45 kb/s and 90 kb/s, respectively.
• Attained up to 800 kb/s with prototype transducers over 0.7 m, extending to 1.2 m (BPSK) and 1.1 m (QPSK) at lower rates.

Conclusions:

• Airborne ultrasound is a promising technology for secure, high-speed indoor wireless communication.
• Advanced modulation techniques and channel estimation enable robust ultrasonic data transmission.
• Ultrasonic systems offer a secure alternative to RF, mitigating risks of remote signal interception.