Implementation of a Spread-Spectrum Acoustic Modem on an Android Mobile Device.

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Sherlock, B.; Neasham, J.A.; Tsimenidis, C.C., “Implementation of a Spread-Spectrum Acoustic Modem on an Android Mobile Device” in OCEANS 2017 – Aberdeen , vol., no., pp.1-9, 19-22 June 2017

doi: TBD

Abstract: Underwater acoustic modems can be expensive and inflexible. Software-defined underwater modems provide flexibility to modify the protocols and modulation schemes. The motivation of this research is towards producing minimal cost, low-power systems. The focus in this paper being the concept of a surface receiver consisting of a hydrophone plugged into a mobile device such as a smart phone or tablet. Applications could be where data or diagnostics are required from a distributed network of underwater sensors in the field that incorporate an integrated acoustic modem. Spread-spectrum signals with large bandwidth-time products are considered including binary orthogonal keying (BOK) using linear frequency modulated (LFM) chirps (Chirp-BOK) and pseudorandom noise m-ary orthogonal code keying (PN M-OCK). Bandwidth of 8 kHz to 16 kHz is utilised for simulated performance of the modulation schemes. The modulation schemes target low-power, low-received-SNR applications with rates between 23.4 bit/s and 375.7 bit/s, targeting a BER of 10-4 at received-SNR of -14 dB to -6 dB respectively. A receiver structure design is implemented on an Android mobile device with experimental validation carried out in a marina over a 100m range. The receiver application was able to successfully demodulate, error-free, all packets received in real-time with received SNR of 34 dB. The receiver modulation scheme was user-selectable at run-time. Recordings from the marina trials were combined with AWGN for varying SNR. These were played into the mobile device for real-time demodulation and showed the mobile device and receiver application produced the target BER of 10-4 for SNRs of -12 dB to 0 dB for the rates 23.4 bit/s and 375.7 bit/s respectively.

Published at: TBD

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Signal and Receiver Design for Low-Power Acoustic Communications Using M-ary Orthogonal Code Keying.

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Sherlock, B.; Tsimenidis, C.C.; Neasham, J.A., “Signal and receiver design for low-power acoustic communications using m-ary orthogonal code keying,” in OCEANS 2015 – Genova , vol., no., pp.1-10, 18-21 May 2015

doi: 10.1109/OCEANS-Genova.2015.7271500

Abstract: Low-power, low received signal-to-noise-ratio (SNR) signals have potential for reducing the impact on marine life from acoustic communications. Here we explore the use of bandlimited pseudo-noise m-ary orthogonal code keying (M-OCK) scheme using m-sequences. Analysis and simulation of receiver structure for synchronisation and data demodulation performance is carried out. Performance of M-OCK is compared with m-ary quadrature amplitude modulation with direct-sequence spread-spectrum (M-QAM DSSS). Real-world channel experiments are carried out with transmission power for the M-OCK sequences limited to less than 1 W acoustic power (170.8 dB re 1 μPa at 1 m) and transmission range varied from 100 m to 10 km in the North Sea. Synchronisation at 10 km is achieved with effective received signal-to-noise-ratio of less than -9.96 dB, and data demodulation of 140.7 bit/s raw throughput with pre-coding bit-error-rate (BER) 0.5 × 10-1 (symbol-error-rate (SER) 0.1) and 46.9 bit/s raw throughput with pre-coding BER 0.9 × 10-3 (SER 1.95 × 10-3). Error-free synchronisation and data demodulation is achieved at ranges up to 2 km, demonstrating data rates in excess of 140 bit/s.

Published at: http://dx.doi.org/10.1109/OCEANS-Genova.2015.7271500

Self Archived at: Sherlock-OCEANS2015-Paper-selfhosted