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Roee Diamant , Lutz Lampe, Emmett Gamroth

Low Probability of Detection for Underwater Acoustic Communication Networks. Roee Diamant , Lutz Lampe, Emmett Gamroth. Motivation. LPD not LPI ! Applications: Military – “quite” sonar, UWAC Safety & Environment – regulations are dB/Hz Lack of clear definition – what is LPD? Low SNR?

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Roee Diamant , Lutz Lampe, Emmett Gamroth

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  1. Low Probability of Detection for Underwater Acoustic Communication Networks Roee Diamant, Lutz Lampe, Emmett Gamroth

  2. Motivation • LPD not LPI ! • Applications: • Military – “quite” sonar, UWAC • Safety & Environment – regulations are dB/Hz • Lack of clear definition – what is LPD? • Low SNR? • Blend in noise? • LPD by who? Objective: representation of LPD 2

  3. Methods for LPD UWAC • Direct Sequence Spread Spectrum (DSSS): • random phase [Ling:2010] • Chaotic sequence [Lei:2011] • OFDM – close bands + slow Tx rate [Leus:2008] • Focusing: time reversal [Yang:2008], MIMO [Zhu:2006] Spreading: Dispreading: PSD noise level PSD noise level Frequency Frequency Interceptor: Receiver: 3

  4. Quality Measures • Determine if a comm. System is LPD • Alternatives: • We use: • captures target Pd, Pfa of interceptor, and Pe of receiver • Not related to Tx power • LPD - for each , define • Truly covert - , Good LPD - 4

  5. LPD Comm. System – a Test Case • Simple attenuation model: • Model used to set upper and lower bounds on LPD! • SNPR at distance r from Tx: • Assuming similar at Rx and In, we get • If are similar : 6

  6. Capabilities: Receiver and Interceptor • Interceptor – energy detection: • Interceptor SNPR (ROC): • Receiver detection (ROC): • Receiver decoding: 7

  7. Simulation • Parameters: • MPSK DSSS vs. Energy detector Channel Parameters Spreading factor 8

  8. Sea Trial • Vancouver Island - Saanich Inlet • Vessels: • Transmitter – fixed buoy (Ocean Technology Test Bed, UVIC) • Receiver – drifting vessel • Interceptor– maneuvering vessel • Procedure: • Find Tx-Rx range (max s.t. BER = 0) • Find Tx-In range (max s.t. detect) 9

  9. Sea Trial - Results Fc = 40kHz Fc = 30kHz • True LPD is possible! 10

  10. Summery • Channel Effect: • LPD inversely proportional to carrier frequency ( ) • LPD better in shallow water ( ) • Communication Effect: • LPD increases with spreading factor (K), • LPD decreases as Tx rate increase • LPD inversely proportional to number of symbols (N) • True LPD is possible! (validated in sea trial) Thank you! 11

  11. Reference • J. Ling, H. He, J. Li, W. Roberts, and P. Stoica, “Covert underwater acoustic communications: Transciever structures, waveform designs and associated performances,” Journal of Acoustical Society of America, vol. 128, no. 5, p. 2898-2909, Nov. 2010. • L. Lei and F. Xu, “A chaotic direct sequence spread spectrum communication system in shallow water,” in International Conference on Control, Automation and Systems Engineering (CASE), Singapore, Jul. 2011. • G. Leus, P. Walree, J. Boschma, C. Franciullacci, H. Gerritsen, and P. Tusoni, “Covert underwater communication with muliband OFDM,” in IEEE OCEANS, Quebec City, Canada, Sep. 2008. • W. Zhu, B. Daneshrad, J. Bhatia, and K. Hun-Seok, “MIMO systems for military communications,” in IEEE Military Communications Conference (MILCOM), Washington, DC, Oct. 2006. • T. Yang and W. Yang, “Performance analysis of direct-sequence spread-spectrum underwater acoustic communications • with low signal-to-noise-ratio input signals,” Journal of Acoustical Society of America, vol. 123, no. 2, pp. 842–855, Feb. 2008. • S. Blunt, J. Metcalf, C. Biggs, and E. Perrins, “Perforamncecharectaristics and metrics for intra-pulse radar-embedded communication,” IEEE J. Select. Areas Commun., vol. 29, no. 10, pp. 2057–2066, Dec. 2011. • P. Walree, T. Ludwig, C. Solberg, E. Sangfelt, A. Laine, G. Bertolotto, and A. Ishøy, “UUV covert acoustic communicatios,” in Underwater Defence Technologies (UDT), Hamburg, Germany, 2006. • C. Liao and T. Woo, “Adaptation from transmission security (TRANSEC) to cognitive radio communication,” in Advances in Cognitive Radio Systems. InTech, 2012, pp. 81–104. 12

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