TEAM 1904 – Final Presentation TEAM 1904 – Final Presentation TEAM 1904 – Final Presentation TEAM 1904 – Final Presentation Enhancing Software Defined Radios for Underwater Acoustic Modem Enhancing Software Defined Radios for Underwater Acoustic Modem Enhancing Software Defined Radios for Underwater Acoustic Modem Enhancing Software Defined Radios for Underwater Acoustic Modem Sponsor The MITRE Corporation Sponsor The MITRE Corporation Sponsor The MITRE Corporation Sponsor The MITRE Corporation Faculty Advisor Dr. Peter Willett Faculty Advisor Dr. Peter Willett Faculty Advisor Dr. Peter Willett Faculty Advisor Dr. Peter Willett Team Members Hunter Malboeuf (EE), Davis Meissner (EE), Greg Palmer (CMPE) Team Members Hunter Malboeuf (EE), Davis Meissner (EE), Greg Palmer (CMPE) Team Members Hunter Malboeuf (EE), Davis Meissner (EE), Greg Palmer (CMPE) Team Members Hunter Malboeuf (EE), Davis Meissner (EE), Greg Palmer (CMPE)
00 Outline
Outline 1. Project Goal 2. Background of Underwater Communications 3. Project Requirements 4. Project Components 5. Communication Design Elements 6. Project Overview and Conclusion a. Simulation b. Hardware Integration c. Analysis of System Performance 7. Remaining Schedule 3
01 Project Goal
Project Goal ● Develop an underwater acoustic communication system using two Software Defined Radios ● Initial goal is one-way SDR communication system ● Stretch goal #1 is to add decision feedback equalizer ● Stretch goal #2 is a two-way SDR real-time communication system ● Three phases: ○ Simulation in MATLAB and C++ ○ Hardware Integration ○ Analysis of System Performance 5
02 Background
Background • Over 70% of the earth is covered by water • The ocean is a 3 dimensional space - 11,000 meters at its deepest • Only 2-3% is explored 7
Applications Manned Vehicles ○ Small research submarines ○ Large military platforms Unmanned Vehicles ○ Autonomous underwater vehicles ○ Remotely operated vehicles ○ Hybrid underwater vehicles 8 8
Why Acoustic Communications? ● Radio Frequencies (~1m range) ○ Absorbed by seawater ● Light (~100m range) ○ Strong dependence on water clarity ● Ultra Low Frequency RF (~100 km) ○ Massive antennas (kilometers long) ○ Not practical outside of government use ● Cables ○ Expensive to lay & impractical for mobile units ● Acoustic Communications (~1 km) ○ Affordable, low power, and well studied 9
Underwater Communication Challenges ● Multipath effects – transmitted messages bounce off the sea surface and bottom, arriving at the receiver at different points in time ● Power losses over the path depend on water temperature and depth of operation for the transmitter and receiver ● Doppler spreading due to transmitter and receiver motion *Controlled environment of this project allows for AWGN channel to approximate some of these effects 10
03 Project Requirements
Project Requirements ● Transmit and Receive small text messages in underwater environment ○ Using ASCII encoding for text, but potential to extend to other types of data (.jpg, etc … ) ● Focus on Waveform Development ○ Modulate using differential phase shift keying (DPSK) ○ Error correction to compensate for errors caused by channel ○ Interleaving to redistribute bits across waveform ○ Synchronization between transmitter and receiver to determine start of message signal. 12
Differences from Previous Years ● 2017 ○ Used BPSK modulation in GNURadio ○ Different synchronization system ○ No error detection or correction ○ No equalization ● 2018 ○ Developed channel emulator to model effects of the underwater system on the signal. ● 2019 ○ DPSK modulation (C++) with error detection, correction, synchronization 13
04 Project Components
Components • Three Ettus X310 Software Defined Radios • Preamplifier (for received signal) • 30 dB Attenuator Ettus X310 Software Defined Radio [1] 15 15
Components • Host machines to interface between SDRs: - Three embedded processors (Udoo X86) *Components are MITRE provided so Udoo X86 Embedded Processors [1] budget is not a concern for the project 16
Current Hardware Setup Transmitter Host Display Receiver Host Display HDMI HDMI UDOO Processor UDOO Processor Ethernet Ethernet Signal Transmission Ettus X310 Ettus X310 Over Coaxial Wire Transmitter Receiver [7] 17
Transmitter Host Display Receiver Host Display HDMI HDMI UDOO Processor UDOO Processor UDOO Processor Ethernet Ethernet Coaxial Wire Coaxial Wire Ettus X310 Transmitter Channel Emulator Ettus X310 Receiver 18
05 Communication Design Elements
Block Diagram Transmit Chain Error Control Permutation/ Frequency Signal Source Compression Modulation Carrier Shift Coding Interleave Shaping Channel Effects/ Transmission Receive Chain Reverse Equalization / Received De- Matched Carrier Decoding Permutation/ Bit Decision Matched Signal compression Filtering Removal Interleave Filtering - only if time permits - complete - to be completed 20
Compression TRANSMIT ● Encodes information into fewer bits than the original message ● Source encoding will be done before our message signal is sent ● Source decoding is applied after the signal is received ● Lempel Ziv possibility ○ may not be of much benefit for our small data and ASCII messages 010100111001010011010 010100111001010011010 Error Control Permutation/ Frequency Compression Modulation Carrier Shift Coding Interleave Shaping 21 21
Begin Message Send TRANSMIT Error Control Permutation/ Frequency Compression Modulation Carrier Shift Coding Interleave Shaping 22 22
Error Coding Control TRANSMIT ● Detect & correct errors that occurred during transmission ● Hamming Code (7, 4) ● Single bit cyclic redundancy parity check validates overall message Error Control Permutation/ Frequency Compression Modulation Carrier Shift Coding Interleave Shaping 23 23
Interleaving TRANSMIT To mitigate against sporadic bursts of noise, interleaving is used Original data: 00000000111111110000000011111111 Interleaved: 01010101010101010101010101010101 This way corrupted bits are more often able to be recovered from the Hamming encoding scheme. Matrix interleaving in a 22 by 22 array is used. Error Control Permutation/ Frequency Compression Modulation Carrier Shift Coding Interleave Shaping 24 24
Coding/Interleaving TRANSMIT Error Control Permutation/ Frequency Compression Modulation Carrier Shift Coding Interleave Shaping 25 25
Modulation TRANSMIT • Varying our waveform with the information in our message by modulating our carrier signal • Replaced original BPSK modulation with a noncoherent Differential Phase Shift Keying (DPSK) scheme • Constant phase represents a “0”, while a shift of 180° represents a “1” [2] Example of DPSK from tutorialspoint.com modulation of our waveform viewed in the oscilloscope Error Control Permutation/ Frequency Compression Modulation Carrier Shift Coding Interleave Shaping 26 26
Frequency Shaping • Root Raised Cosine Filter • Current use in our code was provided by MITRE, not applicable to C++ • Used to reduce intersymbol interference [3] Frequency response of raised cosine filters wikipedia.com Error Control Permutation/ Frequency Compression Modulation Carrier Shift Coding Interleave Shaping 27 27
Synchronization TRANSMIT ● Transmitter and receiver need to establish a synchronized clock to be able to properly interpret any incoming messages ● Transmitter will transmit a preamble chirp signal that is gradually increasing in frequency that the receiver can lock onto and be ready to receive message in sync with the transmitter ● Operating through a correlation function Error Control Permutation/ Frequency Compression Modulation Carrier Shift Coding Interleave Shaping 28 28
Synchronization TRANSMIT ● Chirp signal signal currently sweeps from 12 kHz to 16 kHz over 2.5 milliseconds Error Control Permutation/ Frequency Frequency Compression Modulation Carrier Shift Coding Interleave Shaping Shaping 29 29
Carrier Shift TRANSMIT • Stretching or compression of waveforms in transmission • Doppler effect from transmitter and receiver moving [4] Doppler effect kisspng.com Error Control Permutation/ Frequency Compression Modulation Carrier Shift Coding Interleave Shaping 30 30
Transmission Transmitter Receiver Channel Emulator Channel Effects/ Transmission 31 31 31
synchronizationc Transmission Transmit: • 14 kHz carrier frequency ○ chirp • Sampling rate: 480 kHz ○ gap • Symbol rate: 4 kHz ○ payload data • 120 samples per symbol Channel Effects/ Transmission 32 32 32
Carrier Removal • Stretching or compression of waveforms in transmission • Doppler effect from transmitter and receiver moving [4] Doppler effect kisspng.com Reverse Received De- Equalization/ Matched Carrier Decoding Permutation/ Bit Decision Signal compression Filtering Matched Filter Removal Interleave 33 33
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