Full-Duplex Airborne Ultrasonic Data Communication Using a Pilot-Aided QAM-OFDM Modulation Scheme

Area of Science:

• Wireless Communication
• Acoustic Engineering
• Signal Processing

Background:

• Orthogonal Frequency Division Multiplexing (OFDM) is vital for broadband wireless due to efficiency and multipath immunity.
• Air-coupled ultrasonic communication offers a wireless alternative but faces challenges.

Purpose of the Study:

• Investigate Quadrature Amplitude Modulation (QAM) and OFDM for air-coupled ultrasonic communication.
• Enhance OFDM performance by addressing phase noise and optimizing data rates.

Main Methods:

• Utilized broadband capacitive ultrasonic transducers with high-k dielectric layers.
• Implemented a pilot-aided algorithm for OFDM phase noise correction.
• Developed an ultrasonic propagation model including atmospheric absorption, beam divergence, and transducer response.

Main Results:

• Achieved a system data rate of 400 kb/s with 2 b/s/Hz spectral efficiency.
• Validated simulations against experimental results, showing good agreement.
• Extended error-free transmission range up to 2.5 m using adaptive modulation and up to 1.5 m in full-duplex mode (0.8 Mb/s).

Conclusions:

• OFDM is effective for air-coupled ultrasonic communication.
• Pilot-aided phase noise correction and adaptive modulation enhance system performance and range.
• The developed model accurately predicts ultrasonic signal propagation for system design.