Asynchronous Chirp Slope Keying for Underwater Acoustic Communication

Area of Science:

• Underwater acoustics
• Digital communication
• Signal processing

Background:

• Traditional acoustic communication systems often require preambles for synchronization, increasing overhead.
• Error correction coding adds complexity and latency.
• Efficient data transmission in underwater environments remains a challenge.

Purpose of the Study:

• To develop a preamble-free physical layer technique for acoustic data transmission.
• To enable efficient mapping of short bit sequences using acoustic chirps.
• To assess the performance of the proposed method in realistic channel conditions.

Main Methods:

• Proposed asynchronous acoustic chirp slope keying (aCSK).
• Introduced a symbol detection scheme using superposed matched filter results for preamble-free symbol synchronization.
• Validated performance through laboratory pool measurements and simulations including Rayleigh fading and AWGN.

Main Results:

• In single-band mode (TB=50), achieved 100 bit/s with BER < 0.001 at SNR > -6 dB.
• In dual-band mode (TB=25), achieved 200 bit/s with BER < 0.001 at SNR > 0 dB.
• Simulated packet error rates correlated with BER, increasing with packet length.

Conclusions:

• Asynchronous acoustic chirp slope keying offers an efficient preamble-free communication method.
• The proposed symbol detection scheme effectively removes the need for preambles.
• The system demonstrates robust performance in simulated underwater acoustic channels.