Team Members Hunter Malboeuf (EE), Davis Meissner (EE ... · TEAM 1904 – Final Presentation...

TEAM 1904 – Final PresentationEnhancing Software Defined Radios for Underwater Acoustic Modem

Sponsor The MITRE CorporationFaculty Advisor Dr. Peter Willett

Team Members Hunter Malboeuf (EE), Davis Meissner (EE), Greg Palmer (CMPE)

Enhancing Software Defined Radios for Underwater Acoustic Modem









TEAM 1904 – Final Presentation

Outline

00

3

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

Project Goal

01

5

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

Background

02

7

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

8

Unmanned Vehicles

○ Autonomous underwater vehicles

○ Remotely operated vehicles

○ Hybrid underwater vehicles

Manned Vehicles

○ Small research submarines

○ Large military platforms

Applications

8

9

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

10

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

Project Requirements

03

12

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.

13

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

Project Components

04

15

Components

• Three Ettus X310 Software Defined Radios

• Preamplifier (for received signal)

• 30 dB Attenuator

Ettus X310 Software Defined Radio [1]

15

16

Components

• Host machines to interface between SDRs:

- Three embedded processors (Udoo X86)

*Components are MITRE provided so budget is not a concern for the project

Udoo X86 Embedded Processors [1]

17

Current Hardware Setup

Signal Transmission Over Coaxial Wire

UDOO Processor UDOO Processor

Receiver Host DisplayTransmitter Host Display

HDMI HDMI

Ethernet Ethernet

[7]

Ettus X310 Transmitter

Ettus X310 Receiver

UDOO Processor

18

Ettus X310 Transmitter Ettus X310 ReceiverCoaxial Wire

UDOO Processor

Receiver Host DisplayTransmitter Host Display

HDMI HDMI

Ethernet Ethernet

Channel EmulatorCoaxial Wire

UDOO Processor

Communication Design Elements

05

20

Block Diagram

Signal Source Error Control Coding

Permutation/Interleave Modulation Frequency

Shaping Carrier ShiftCompression

Channel Effects/Transmission

Carrier RemovalBit Decision

Reverse Permutation/Interleave

DecodingDe-compression

ReceivedSignal

Matched Filtering

- only if time permits

- complete

- to be completed

Equalization / Matched Filtering

Transmit Chain

Receive Chain

21

Compression

● 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

Error Control Coding



010100111001010011010

010100111001010011010

21

TRANSMIT

22

Begin Message Send




22

TRANSMIT

23

Error Coding Control

● Detect & correct errors that occurred during transmission

● Hamming Code (7, 4)

● Single bit cyclic redundancy parity check validates overall message




23

TRANSMIT

24

Interleaving

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.




24

TRANSMIT

25

Coding/Interleaving




25

TRANSMIT

26

Modulation




• 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

26

TRANSMIT

modulation of our waveform viewed in the oscilloscope

27

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 filterswikipedia.com

27

28

Synchronization




● 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

28

TRANSMIT

29

Synchronization




● Chirp signal signal currently sweeps from 12 kHz to 16 kHz over 2.5 milliseconds

Frequency Shaping

29

TRANSMIT

30

Carrier Shift




• Stretching or compression of waveforms in transmission• Doppler effect from transmitter and receiver moving

[4] Doppler effect kisspng.com

30

TRANSMIT

31

Transmission

31


31

Transmitter Receiver

Channel Emulator

32

Transmission

32


32

• 14 kHz carrier frequency• Sampling rate: 480 kHz• Symbol rate: 4 kHz• 120 samples per symbol

Transmit:○ chirp○ gap○ payload data

synchronizationc

33

Carrier Removal

• Stretching or compression of waveforms in transmission• Doppler effect from transmitter and receiver moving

[4] Doppler effect kisspng.com

33




ReceivedSignal

Matched FilteringEqualization/Matched Filter

34

Synchronization

34

● Used a correlation function to look for our chirp signal in our received data

● Used sine and cosine version of chirp

● A spike occurs at a location indicating a chirp signal was found

RECEIVE




ReceivedSignal


Graph of correlation values

35

Decision Feedback Equalizer (Stretch Goal)

hn

= hn-1

- μ(d(n)-q(n))pn

● Receiver gets signal from direct path and multiple reflection paths● Objective is to account for the addition and cancellation in our waveform● Send known data bits, account for difference in receiver and adjust for payload

35

RECEIVE




ReceivedSignal


36

Bit Decision

• Input received message signal

• Duplicate signal• Multiply by sine and

copy by cosine• Take an amount of

samples for next symbol• Sum to make bit

decision

36

RECEIVE




ReceivedSignal


37

Deinterleave

37

RECEIVE




ReceivedSignal


Received data: 01010101010101010101010101010101

Deinterleaved data: 00000000111111110000000011111111

38

Decoding

38

RECEIVE




ReceivedSignal


● Hamming Code (7, 4)

● Detect & correct errors that occurred during transmission and replace the incorrect bits

● Remove parity bits

3939

RECEIVE




ReceivedSignal


Decoding / Received Message

Project Overview and Conclusion

06

41

Simulation

● MATLAB model has been modified to:○ Read data from a text file○ Encode data to ASCII characters to bits○ Apply Hamming (7,4) Code and CRC single bit error correction○ Use matrix interleaving for bit redistribution before transmission○ Use chirp signal and correlation to find start of message ○ Transmit over AWGN channel ○ Recover and decode original data

41

42

Simulation

● C++ model has been modified to:○ Read data from a text file○ Encode data to ASCII characters to bits○ Apply Hamming (7,4) Code and CRC single bit error correction○ Use matrix interleaving for bit redistribution before transmission○ Use chirp signal and correlation to find start of message ○ Transmit over AWGN channel ○ Recover and decode original data

42

43

Simulation

● Changes to MATLAB model since Fall final presentation:○ Added single bit CRC to validate overall message○ Added chirp signal for synchronization○ Adding DFE○ MITRE provided us a new channel emulator in MATLAB

43

44

MATLAB Output

- No encoding used * Hamming(7,4) and Interleaving used

BPSK

44

45

Hardware Integration - C++ Status

● Completed porting over MATLAB functions○ Interleaving / Deinterleaving○ Error Detection / Correction with Hamming

Encoding and CRC○ DPSK Modulation / Demodulation ○ Synchronization

● Stretch goals○ DFE implementation○ Add hardware channel emulator

45

46

Analysis of Received Waveform

● Relevant quantities that will be extracted from data include:○ Bit error rate (BER)○ Signal to noise ratio (SNR)○ Actual data transmission and reception rates

● Third SDR and processor will be used to apply channel effects○ Test theoretical operation of C++ code before water testing

● Lab data can compared to MATLAB and channel emulator results

46

47

Experimental Difficulties

● Learning C++○ bugs, crashes, syntax

● Spent a day troubleshooting a bad cable● Relearning how to use oscilloscope functions● Using convolution instead of correlation● USRP doubling carrier modulation● Exporting data from Linux on Udoo board to Matlab on PC

47

48

Stretch Goals

● DFE implementation● Test MATLAB using channel emulator● Test hardware using channel emulator

48

49

Sponsor Contact

● Visited MITRE on November 19th to tour facility and obtain hardware○ Learned to operate embedded processors and SDRs

● Received hardware integration C++ code in late January● Received static MATLAB channel emulator in mid March● Received C++ channel emulator for third SDR recently.● We’ve been holding regular weekly meetings with MITRE and

Professor Willett to discuss status updates

49

50

Demo Day Plan & Final Deliverables

● Poster displaying:○ General overview of process○ MATLAB Performance figures○ C++ Performance figures SNR, BER

● Demonstration:○ Transmit a message through the hardware channel emulator

● Deliverable: One-way DPSK communication system○ MATLAB simulation Code○ C++ hardware Code○ Final Report

50

Schedule

07

5252

QUESTIONS?

Works Cited[1] MITRE. 2019 Senior Design Project Outline

[2] DPSK Image from Tutorials Point https://www.tutorialspoint.com/digital_communication/digital_communication_differential_phase_shift_keying.htm

[3] Raised Cosine Filter Image https://en.wikipedia.org/wiki/Raised-cosine_filter

[4] Doppler Effect Image https://www.kisspng.com/png-relativistic-doppler-effect-doppler-radar-wave-spe-919067/preview.html

[5] Globe image https://scienceline.org/2017/04/protecting-two-thirds-globe/

[6] DFE Image https://www2.eecs.berkeley.edu/Pubs/TechRpts/2017/EECS-2017-112.pdf

[7] Ubuntu Machine https://www.ubuntu.com

Date post:	30-May-2020
Category:	Documents
Upload:	others
View:	2 times
Download:	0 times

Team Members Hunter Malboeuf (EE), Davis Meissner (EE ... · TEAM 1904 – Final Presentation...

Documents