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© WiNES 2014 @ Northeastern University COE Lab Fair 2014 1 10 100 500 0.5 10 −5 10 −4 10 −3 10 −2 10 −1 10 0 Frequency [kHz] Absorption Coefficient [dB/m]) Fisher − Simmons Absorption Thorp Absorption Electromagnetic RF Waves Propagate through conductive salty water only at 30-300Hz Require large antennae and high transmission power Optical Waves Affected by scattering Directional: high precision in pointing narrow laser beams High-data rate, short-distance communications Acoustic Waves Used in military and civilian underwater communication systems Low data rates, long distance communications Underwater Acoustic Networks Emrecan Demirors and Tommaso Melodia Department of Electrical and Computer Engineering Northeastern University, Boston, MA, USA E-mail: {edemirors, melodia}@ece.neu.edu Why Underwater Networks ? Challenges of Acoustic Channel How to Establish Wireless Communications Underwater? Architecture of Our Underwater Testbed Distributed Tactical Surveillance Surveillance, reconnaissance, targeting and intrusion detection with AUVs and sensors Military and civilian Environmental Monitoring Pollution monitoring (chemical, biological) Monitoring of ocean currents and winds detecting climate change, understanding human activities on marine ecosystems Equipment Monitoring Prevent failures in underwater equipment (Oil & Gas industry) Valve failure led to oil spill in the Gulf of Mexico Disaster Prevention Sensor networks that measure seismic activity from remote locations and provide tsunami warnings to coastal areas Future Work The Internet Underwater Software-defined Underwater Modem [1] T. Melodia, H. Kulhandjian, L. Kuo, and E. Demirors “Advances in Underwater Acoustic Networking,” in S. Basagni, M. Conti, S. Giordano, and I. Stojmenovic, editors, Mobile Ad Hoc Networking: Cutting Edge Directions, pages 804{852. John Wiley and Sons, Inc., Hoboken, NJ, second edition edition, 2013. [2] E. Demirors, G. Sklivanitis, G. E. Santagati, T. Melodia, and S. N. Batalama “Design of A Software-defined Underwater Acoustic Modem with Real-time Physical Layer Adaptation Capabilities,” submitted to ACM Conference on Underwater Networks and systems (WUWNet), 2014. [3] Y. Sun, T. Melodia ”The Internet Underwater: An IP-compatible Protocol Stack for Commercial Undersea Modems," in ACM Conference on Underwater Networks and systems (WUWNet), 2013. Field and Laboratory Tests References Slow propagation of sound waves in water 1500 m/s vs. 3e8 m/s for RF waves Reduce the network throughput considerably Large propagation delay variance Prevents accurate estimation of the round-trip-time Strong multipath and Doppler spread Inter-symbol-interference Complex receiver design Noise Man-made Noise Machinery (pumps, reduction gears, power plants) Shipping Activity Ambient Noise Biological and Seismic activities Hydrodynamics (waves, currents, tides, rain, wind) Transmission (Path) Loss Geometric Spreading: Spreading of sound waves Absorption Coefficient Caused by conversion of acoustic energy into heat Frequency and distance dependent High bit error rates and losses of connectivity Underwater sensors prone to failures (fouling and corrosion) Transmit energy (1-20 W) is 100 times higher than in wireless sensor networks Available bandwidth severely limited Limited Battery power limited and challenging to recharge Developing and implementing new communication protocols for underwater acoustic networks Demonstrating the capabilities of the proposed SDR modem in cognitive/security problems underwater Developing new protocols for localization and time- synchronization Need for a reconfigurable, agile, and intelligently- flexible autonomous radios to implement runtime- adaptive communication protocols. A networking architecture for commercial underwater modems that is compatible with traditional TCP/IP Applications Access underwater nodes from any Internet-connected device (e.g., smartphones, workstations) Reconfigure UWA networks through SSH or FTP Monitor and diagnose networks in real-time Experiments Transfer Data/Message from UW nodes to Internet devices (PC/ smartphone) Access UW nodes using SSH from our workstations Establish TCP connection by recompiling Linux Kernel (Increase the TCP initial retransmission timeout) Create a firewall at the NAT gateway to secure access to our UW network This research has been featured in media; Modem Architecture USRP N210 and host Machine Power Amplifier, Voltage Preamplifier, and Electronic Switch Acoustic Transducer Direct path Surface reflections Bottom reflections 10 −3 10 −2 10 −1 10 0 10 1 10 2 10 3 0 10 20 30 40 50 60 70 80 90 100 110 Frequency [kHz] Noise Power Spectrum Level [dB re 1 μPa] Thermal Noise (N th ): Shipping Noise (N s ): Heavy Moderate Light Wind Noise (N w ): 2.5 m/s 1 m/s 12 m/s 7 m/s Turbulence Noise (N t ): Shared, reconfigurable platform UDB-9000 universal deckbox with acoustic transducer 11 Telesonar SM-75 modems one sonar modem SM-75 modem UDB-9000 Universal deckbox Test Tank and Pool Lake LaSalle at University at Buffalo Lake Erie, Buffalo, NY Physical Layer Adaptation PHY layer implementation on GNU Radio and Matlab OFDM PHY layer parameter adaptation (adaptive modulation and coding) Seamless switch between different communication technologies (i.e., OFDM and DS-SS) Robust feedback link based on a binary chirp spread spectrum modulation (B-CSS) PHY LNK Underwater Network Interface CSMA/NAV ARQ/c-ACK ADP Header Comp Router Proxy Packet Frag NET Mesh Router Exterior Routing ICMP(v6) ARP TRN UDP TCP APP FTP SSH DHCP(v6) ... First ever Underwater Tweet
