Subsea Communications

Transcription

1 Subsea Communications FINAL PRESENTATION Subsea Systems TAC Daniel Sexton GE Global Research Arsen Zoksimovski Northeastern University

2 Motivation Subsea Wireless Communications Improved productivity of Subsea production fields through enabling technologies, Subsea Asset Intelligence, Equipment Health Monitoring and Maintenance. Eliminate connectors and improve system reliability. Speed deployment, enable cost efficient retrofits. Cross cutting technology with benefits to DOE and DHS Objectives Robust and adaptive high h speed wireless communications Small antenna size Resistant to subsea environmental issue (turbidity, fouling, multipath) Riser Health Monitoring Subsea Production Asset Optimization ROV Communications i

3 Acoustic & Optical Communications At Depths Where Sunlight Penetrates, Marine Growth Will Occlude Optics High Rate Acoustic Communications suffer from multipath, delays and noise. Acoustics impact aquatic life ecological l controversy Marine Growth Acoustics 200m 1000m Optical Multipath

4 Underwater Communications Optics: clear, deep, water Acoustics: long range, low speed RF: high attenuation, but no shadow zones Near field: Magnetic: Large loop antennas, limited range, narrow bandwidth. Electric Field: Small contacts, limited range, wide bandwidth, GRC/NEU approach.

5 Wireless using RF Conduction Applications: Robust communication modems that can be used for a variety of applications: Remote Sensing on Manifolds Wet connections for data communications ROV communications and guidance Production Risers Subsea ROVs

6 RPSEA Project Status Transmitter/Receiver prototyped Channel capacity (theoretical) completed Receiver demodulation algorithm completed Lab tested in salt water tank Field Experiment conducted in May 2011 (Transmitter/Receiver i deployed d under water) High speed (5 MBPS) demonstrated (10cm distance).

7 Lab Setup -NEU Receiver Transmitter Multi-carrier (OFDM) modulation, 128 sub carriers 5Mbps transmitted

8 Prototype Hardware Transmitter Receiver Input LNA DAC Lin. Tech. Data Capture Lin. Tech. To Fiber Optic Modem Clock

9 Sea Trials Small Boat used for sea trials off of Nahant MA. 40 foot water depth. Experiment ~ 15 feet under water. Sea water conductivity 4.3S/M

10 Transmitter Characteristics For our tests, we designed an OFDM communication system that included: Nsc = 128 Subcarriers Total BW=6.25 MHz Lowest Frequency = 100 khz Subcarrier Spacing = khz Sampling Frequency = 50 MHz Symbol Duration = fs /BW* N sc = 1024 samples Modulation: BPSK or QPSK on all subcarriers

11 Technology Timeline High speed/short range data transmission demonstrated in relevant environment and within the limits of the equipment. Prototype did not support transmission near the channel capacity predicted. Further experiments would extend the data rate to 30Mbps. 2009: Trial in large tank, 500kbps 2011: Trial in shallow Ocean 5Mbps Future: Trial in Deep Ocean 30Mbps

12 Technology Limits Channel Transfer Function Channel Noise Distribution Given the Channel attenuation and channel noise characteristics Channel capacity is 113Mbps at 1mw transmit power Note: Maximum capacity is not achievable. 30 to 50mbps is more realistic.

13 Remaining Tasks Final Report Nov Revisit the theoretical propagation model and refine for better estimation. Extend simulation analysis to include various boundary conditions and objects within the signal propagation space representative of real installations Extend channel capacity analysis to include effects of imperfect channel estimation.

14 System Design Challenges Next phase project would address: Low noise amplifier design for low frequency operation. Optimizations for input impedance matching for various salt water conditions. Antenna optimization for specific applications. Higher efficiency transmitter. Adaptive channel coding. Extending the number of subcarriers from 128 to Complete required testing and evaluations to reach TRL 5. Sea Trials in various conditions Data Collection and assessment