A High-Speed High-Frequency Broadband Acoustic Modem for Short-to-Medium Range Data Transmission in Ports, Very Shallow Waters and Deep Waters Using Spread-Spectrum Modulation and Decision Feedback Equalizing
Final rept., 1 Aug 2005-6 Feb 2006
FLORIDA ATLANTIC UNIV BOCA RATON
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Testing of a high-resolution decision feedback equalizing with parallel tracking of large Doppler algorithm developed at FAU by Prof. Beaujean The long-term objective is the commercialization of a high-speed high-frequency acoustic modem transmitting data at true rates of up to 105,000 bps, at a maximum range of 500 m and operate between 240 kHz and 380 kHz. Acoustic communications were achieved at a coded rate up to 150,000 bps at a range of 50 m. At 75 m, acoustic communication was possible up to 50,000 bps coded, due to limitations of the source power amplifier. Accurate Doppler correction and sufficient SNR were required to perform broadband underwater acoustic communications at high frequencies. Results observed at 75 m under adverse conditions in terms of Doppler and SNR 4 dB indicated that the BPSK modulation still provides acceptable results using 20 micros and 40 micros symbols. The results were obtained using an output power of 0.63 W, which showed that the modem was remarkably power efficient and ideal for small UUVs and divers, as it achieves 130,692 bitsJ at 150,000 coded bps.
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