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ECE Team 17:UDT - Final Presentation
Students: Ryan Harvey, Kiran Nadkarni, Harris Yousafzai
ECE Faculty: Dr. Necmi Biyikli
Industry Sponsor: General Dynamics Electric BoatContacts: Eric Hultgren, Robert Scala
Underwater Data Transfer Use Cases
- Military communications and tactical surveillance- Pollution monitoring- Undersea oil pipeline control- Climate Change and Oceanography observational tool- Lithospheric Plate observation and study
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Specifications and Constraints- Minimum Accepted Data Transfer Rate: 100 kBps
- Maximum Goal Data Transfer Rate: 1 GBps
- Transfer Quality: 100% No Lost Packets
- Maximum Data Transfer Equipment Current: 3 A
- Maximum Exposed Terminal voltage: 30 VDC
- Materials and components selected must be:
- Corrosion Resistant
- Seawater Capable
- Depth capable for UUV
- Safe for Underwater Life
- Maximum Distance of 30 Ft.
- Operating Temperature of (0°C - 36.6°C)
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Specifications Cont.
- Riptide UUV Specifications
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Source: Electric Boat
Source: Electric BoatTable 1: Specifications of Riptide UUV
Source: Electric BoatFigure 1: Picture of Riptide UUV
System Design Outline
- Optical Communication System- Blue/Violet light
- 10mW - 5W optical transmission power
- Operating Temperature of -5°C - 40°C
- LED/Semiconductor Laser (~405 - 450 nm wavelength)
- Photodiode Receiver
- Microprocessor Choice
- Modulation & Demodulation
- Error Correction
- Potential Amplifier Circuit
- Factors of Data Rate and Information Loss
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Figure 2: Block diagram of system
Simulink Model (cont.)- OOK Modulation Scheme informed by the Digital
Modulators and Demodulators Simulink Fileset by Diego
Barragan
- Data Bits are used as a threshold for determining if the
Carrier wave is sent into the channel
- If the Data bits are greater than 0.5, then the Carrier
frequency is sent out
- Currently the carrier Frequency is multiplied by an ideal
Laser actuation, though a more realistic simulation would
incorporate more complex dynamics
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Figure 3: OOK Modulation Process
Figure 4: OOK Modulation Comparator
Simulink Model (cont.)- OOK Demodulation is also done in accordance
with available Digital Communications Simulink
Diagrams
- The Carrier 1 is used to reconstruct the signal
- FIR filtering is done to remove the impact of the
carrier before removing any signal contributions
less than 0.5
- Currently ideal Photodiode reception is
assumed,
8Figure 6: FIR Filter Magnitude Response
Figure 5: OOK Modulation Process
Simulink Model (cont.)
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- The current simplified
model works to a
significant degree
- The primary issue is that
long strings of constant bit
1 are often broken into
smaller sections
- This would heavily distort
information received and
will require correction
Figure 7: Testing of Simulink System
Challenges to Simulink Implementation- There are two primary challenges we must overcome to produce accurate and effective
simulations of Underwater Optical Wireless Communications:
- Simulation of Underwater Optical Channel Effects
- Simulation of Actuation Dynamics and Controller Performance Dynamics
- The UOWC channel model will likely need to be significantly simplified due to:
- Difficulties with mathematical implementation
- Significant computational complexity required to produce accurate channel behavior
- Current models rely on solutions to the Radiative Transfer Equation (RTE), however most reviews
conclude that these current methods are unlikely to be scalable to networked communications
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Underwater Optical Channel Modeling- UOWC modeling is still very much an active research area.
- Simple analytical models often rely on estimates like Beer’s Law:
- Beer’s Law roughly gives power loss in 1D as a function of distance and the scattering and
absorption constants as a function of wavelength
- This application only works for attenuation due to single scattering events, and can not account for
multiple scattering, time, and non-exact LOS
- These complexities, as well as taking into account computation of absorption and scattering
coefficients and turbulence, produce models which 10+ hours of run time for seconds of accurate
results
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Underwater Optical Channel Modeling- For actual development, more sophisticated models are needed
- Current RTE solution methods include:
- Monte Carlo (simplest to produce and most common but
contains statistical errors and very slow run times)
- Discrete Ordinates (difficult to program, reliant on high
complexity mathematics, speed advantages)
- Invariant imbedding (difficult numerical method, limited to 1D,
significant speed advantages)
- Most papers seem to use Monte Carlo for rough estimation and
then reconstruct empirical data afterwards for fine tuning12Figure 8: Table of Common RTE Methods
Modulation Technologies- Direct Modulation & External Modulation
- Coherent Mod. & Intensity Mod.
- Commonly Used Protocols:- On-Off Keying (ASK)- Pulse Position Modulation- Pulse Width Modulation- Quadrature Amplitude Modulation
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Credit: TutorialsPoint
FEC Channel Coding- Necessary to combat Attenuation of Medium
- Practice of including redundancy into message
- Benefits are seen to Range and Power Use
- Slight Detriment to Maximum Bandwidth
- Commonly Used Coders- Block Codes
- Low Density Parity Check
- Reed Solomon
- Turbo/Trellis Coded Modulation
- Convolutional
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Part List & Budget
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Table 2: Final Part List & Budget
Hardware System Design
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Figure 9: Picture of Transmitter CircuitFigure 10: Picture of Receiver Circuit
Hamming(7, 4) & Manchester Code
1. Nibble is Multiplied by Code Generator Matrix
2. 3 Parity Bits Formed at Front of String From This
3. 8th Bit Added is XOR of Summation of other Bits
4. Each 2 Bytes Paired by Most and Least Significant
5. 2 Start Bits & 1 Stop Bit Added
6. Manchester Signal is the 11 Bits Split Into 22 Half-Bitsa. 1st Half Bit is XORed with “0”
b. 2nd Half Bit is XORed with “1”
7. Pairs of 22 Bits are Modulated as Set of 44 Bits by Laser
8. Hamming Decoding and Manchester Demodulation Occurs
Figure 11: Hamming Encoding Generator MatrixCredit: HobbyTransform
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Figure 12: Manchester Coded SignalCredit: Cleveland State University
Future Work & Improvements
- Use of alternative modulation schemes: OOK, PWM, PPM, QAM, PSK- High Power Lasers
- Lower Net Power than RF & Acoustic Systems- Significantly Higher Distance Possible- Helps combat Line of Sight Issues
- Hybrid or Array Systems to deal with LOS Issues- Receiver Array / Wider FOV Photodiode Receiver
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Current Technology
- MIT Lincoln Laboratory’s Optical Communication AUV
- Implementations with Green Light & Ultraviolet Light
- Sonardyne BLUECOMM 100 & 200 Systems
Figure 14: BlueComm 100 SystemCredit: Sonardyne 19
Figure 13: Lincoln Lab UOWC SystemCredit: MIT Lincoln Lab
Project Management
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Project Management
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References1. Underwater Optical Wireless Communication Oliveira & Salas 2020 REPSOL 2. General Dynamics EB Capstone Project Details3. Sponsor Provided Notional Parameters and Requirements4. Riptide UUV specifications Documentation5. Journal of Optoelectronics and Advanced Materials6. On the Use of a Direct Radiative Transfer Equation Solver for Path Loss Calculation in Underwater Optical Wireless Channels IEEE
Wireless Communications 20157. Diego Barragán (2021). ASK, OOK, FSK, QPSK. Digital Modulations and demodulations in SIMULINK.
(https://www.mathworks.com/matlabcentral/fileexchange/25750-ask-ook-fsk-qpsk-digital-modulations-and-demodulations-in-simulink), MATLAB Central File Exchange. Retrieved March 10, 2021.
8. Encoded-Laser-and-LED-Serial-Communication (https://github.com/HobbyTransform/Encoded-Laser-and-LED-Serial-Communication)
9. Gkoura et. al (July 26th 2017). Underwater Optical Wireless Communication Systems: A Concise Review, Turbulence Modelling Approaches - Current State, Development Prospects, Applications, Konstantin Volkov, IntechOpen, DOI: 10.5772/67915.
10. Laura Johnson et al. (October 2013) A survey of Channel Models for Underwater Optical Wireless Communication11. Saeed, Celik, Al-Naffouri, and Alouini (June 2019) Underwater Optical Wireless Communications, Networking and Localization: A
Survey12. Zhang, Kou, Yang, He and Duan (November 2020) Monte-Carlo-Based Optical Wireless Underwater Channel Modeling with Oceanic
Turbulence - Optics Communications Vol. 475 DOI:10.1016/j.optcom.2020.126214.13. Schirripa Spagnolo, G.; Cozzella, L.; Leccese, F. Underwater Optical Wireless Communications: Overview. Sensors 2020, 20, 2261.
https://doi.org/10.3390/s20082261
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