Acoustic Communications ANCHOR Workshop Feb 27-Mar 1 2006

1. Acoustic Communications ANCHOR WorkshopFeb 27-Mar 1 2006 Lee Freitag Woods Hole Oceanographic Institution Woods Hole, Massachusetts

2. Outline • Communications system design • Applications and Results • High frequency • Medium Frequency • Low Frequency • Networking • Interoperability • Standardization • Recommendations

3. Frequency Regimes VLF LF MF HF VHF Ambient Noise Studies Marine Mammals Typical Communications Band 1-50 kHz Long-Range Navigation Seismic Tomography 0.1 1 10 100 1k 10k 100k Frequency (Hz)

4. Layered Architecture From draft ASTM standard on communications developed by Committee F41, UUVs, with sponsorship from PMS-403 (US Navy).

5. Frequency Regimes VLF LF MF HF VHF Ambient Noise Studies Marine Mammals Typical Communications Band 1-50 kHz Long-Range Navigation Seismic Tomography 0.1 1 10 100 1k 10k 100k Frequency (Hz)

6. UUVs and Scientific Applications

7. Very High-Rate – Shallow Water (15 m) • Test Parameters: • 1.5 km Range • 10 kHz BW • 4 bits per Hertz • 8 channel array (one meter) • 40,000 bps raw, 30,000 bps coded.

9. Previous Results

10. Compressed Pre-stored Sidescan Images Transmitted from REMUS at AUV Fest 2001

11. Two AUV Simultaneous Operation with Acoustic Re-direction for MCM Work Vehicle 2 Path: Re-Acquisition Missions with REMUS equipped with APL-UW Acoustic Lens Initial Holding Pattern Actual Missions Sent Using the Acoustic Modem

12. Frequency Regimes VLF LF MF HF VHF Ambient Noise Studies Marine Mammals Typical Communications Band 1-50 kHz Long-Range Navigation Seismic Tomography 0.1 1 10 100 1k 10k 100k Frequency (Hz)

13. Medium Frequency Example: 6 km • Test Parameters: • 6 km Range • 200 m depth • 1.25 kHz BW • 2 bits per Hertz • 8 channel, 8 m array • 2500 bps raw, 2,000 bps coded.

14. Medium Frequency Example: 44 km • Test Parameters: • 44 km Range • 200 m depth • 1.25 kHz BW • 2 bits per Hertz • 8 channel, 8 m array • 2500 bps raw, 2,000 bps coded.

15. Frequency Regimes VLF LF MF HF VHF Ambient Noise Studies Marine Mammals Typical Communications Band 1-50 kHz Long-Range Navigation Seismic Tomography 0.1 1 10 100 1k 10k 100k Frequency (Hz)

18. VLF Example: AET Tomography Signal 3200 km • Test Parameters: • 3200 km Range • Pacific Ocean • 37.5 Hz BW • 1 bit per Hertz • 20 channel array • 37.5 bps max raw, 0.1-20 bps coded, depending on array.

19. VLF Example: AET Tomography Signal 3200 km • Test Parameters: • 3200 km Range • Pacific Ocean • 37.5 Hz BW • 1 bit per Hertz • 20 channel array • 37.5 bps max raw, 0.1-20 bps coded, depending on array.

20. Interoperability • Physical Layer: WHOI Frequency-Hopping Standard • Low-rate (80 bps) standard for inter-operable modem communications. • Application Layer: Compact Control Language (CCL) • Standardized messages for TIME, POSITION, BATTERY, etc. Surf-Zone Crawler Cetus II Solar AUV: WHOI and Benthos Acoustic Modems Real-Time Data: Two different Modems REMUS Search-Classify-Map

21. Multi-Vehicle Command and Control and Interoperability Multi-vehicle operations using a common acoustic navigation network and common command and control structure at AUV Fest 2003 and 2005 Surf-Zone Crawlers Gateway Buoys Nekton Ranger REMUS AUVs Cetus II Bluefin Sea Lion

22. Compact Control Language Spec. Messages are documented in detail using C-language structures with example hex dumps for use in validation. Example Message Format (Re-Direct) typedef struct { unsigned char mode; // MDAT_REDIRECT unsigned char message_number; LATLON_COMPRESSED lat; // Center of search LATLON_COMPRESSED lon; // Center of search char speed_depth_flags; unsigned short depth_goal_encoded_transit; char speed_encoded_transit; unsigned char device_cmd_transit; //range. unsigned short depth_goal_encoded_survey; char speed_encoded_survey; unsigned char device_cmd_survey; unsigned char num_rows; // 0 if not rows. unsigned short row_length; // in meters unsigned char spacing_0; // in meters unsigned char spacing_1; // in meters char heading_encoded; LATLON_COMPRESSED lat_start; // ack only, where started LATLON_COMPRESSED lon_start; char spare[3]; } MODEM_MSG_DATA_REDIRECT;

23. Example Message: Bathymetry

24. Example Message: Redirect Survey

25. Slow Slow Msg Rate Msg Rate Fast Fast Network Access Protocol Prof. J. Schindall & R. Kanthan • Objectives: • To allow all AUVs to cooperatively communicate and navigate in the field without centralized access control. • Create fair access protocol. • Allow “desperate” node to go first. • Status: Thesis complete & available. 0 % Collided 100 0 % Collided 100 Simple (Greedy) Algorithm 4-Way Handshake Algorithm

26. Different types of networks can be supported on top of multiple modems: Fixed, ad-hoc, etc. Network Type 1 Network Type N Common API allows network development to be independent of modem Standard Acoustic Modem Software API Modem Interface & Driver Modem Interface & Driver Modems Support open, proprietary and Navy-only protocols. Proprietary Modulation N Types Standard Modulation M Types Proprietary Modulation N Types Standard Modulation M Types Acoustic Modem Manufacturer 1 Acoustic Modem Manufacturer P Acoustic Channel Modular Acoustic Communications Vision

27. Recommendations • Confirm draft requirements vis-à-vis: • Platform needs and capabilities (size, etc.) • Development effort (risk) • Infrastructure cost • Operations and Maintenance • Develop functional specification to capture requirements • Describe notional implementation which is: • Modular & Layered • Standardized (interoperable at various levels) • Isolates high-risk & developmental areas

28. Questions?