Optical Voice and Data
Toolkit
ECE4007 Senior Design Final Report
Section L03: Dr. Chris James
Final Report detailing the Optical Voice and Data Toolkit. This
system uses Free Space Optics technology to transmit both
voice and data between two points in direct line of sight.
Neil Gandhi
Chris Hunold
Alex Grubl
12/9/2009
Table of Contents
Executive Summary ...................................................................................................................... 3
1.
Introduction ........................................................................................................................... 4
1.1
Objective ........................................................................................................................ 4
1.2
Motivation ..................................................................................................................... 5
2.
Project Description and Goals .............................................................................................. 5
3.
Technical Specifications ........................................................................................................ 6
4.
Design Approach and Details ............................................................................................... 7
4.1
Design Details................................................................................................................ 7
4.2
Codes and Standards .................................................................................................... 11
5.
Schedule, Tasks, and Milestones ........................................................................................ 11
6.
Results and Acceptance Testing ......................................................................................... 12
7.
Budget and Cost Analysis ................................................................................................... 15
8.
Conclusions and Future Work ........................................................................................... 15
9.
References............................................................................................................................. 18
Appendix A – Full Project Description ..................................................................................... 19
Appendix B – Gant Chart .......................................................................................................... 23
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Executive Summary
The Optical Voice and Data Toolkit is a system that allows communication between two
soldiers on the battlefield through free space using optical light that is both eye safe and covert.
The system proposed allows communication between multiple points with an emphasis on
mobility, security, high-bandwidth connectivity and ease of use. Communication must be
possible in all types of environments and battlefields, including, but not limited to, urban,
suburban, maritime, and wilderness areas. Both line of site and non line of site communication
must be achieved with up-to-date information in real time.
The system developed and designed is a subsystem of the complete Toolkit and will
demonstrate a proof of concept of the technology. Line of site data and voice communication
was focused on between only two points with one point transmitting and the other receiving.
Both data and voice communications was possible over a 20 meter distance in real time with
little latency. The laser used was a 405nm blue laser allowing for greater power and therefore
greater communication distance. The detection of the communication beam is still difficult to
intercept without special equipment and precise knowledge of the beam source and destination.
The estimated cost of the subsystem was approximately $3148.00 in parts alone, not including
time and labor costs. This was only a proof of concept so a marketing analysis was not done, as
the scope of such an analysis is beyond the subsystem. Overall this project demonstrates a novel
way of communication that is secure, fast, and relatively inexpensive to implement.
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1. Introduction
Free space optical communications is a growing field in which light is used as the
primary medium of transmission between two or more points of interest. The client requested a
new method of communication for soldiers on the battlefield making use of this technology. The
Optical Voice and Data Toolkit is a system which allows communication between two points on
the battlefield in both line of sight and non line of sight situations. The system designed is the
line of sight portion of the Toolkit which allows for communication between two soldiers in
direct line of sight. The system costs $3328 dollars in parts to develop and involves only the line
of sight portion of the Optical Voice and Data Toolkit requested by the client.
1.1 Objective
The Optical Voice and Data Toolkit is a system built to allow fast, and secure
communication between two or more points in direct line of sight or non line of sight situations
on the battlefield. The system is required to be modular, allowing for attachments to any scope,
binoculars, or hand held equipment in use today. The system also incorporates a relay station
which would allow interaction with all soldiers connected to the optical network.
Communications must be possible in all types of weather conditions as well as urban, suburban,
wilderness, and maritime environments [1].
The product designed is a subsystem of the total Toolkit. Direct line of sight
communication was focused on with voice communication at a rate 128 kbps and data transfer at
a rate of about 45Mbps at a distance of up 20 meters. The primary customer for this system is the
military and Department of Defense, both of which require up-to-date tactical information spread
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amongst its members in a fast and secure way. The original project description can be found in
Appendix A.
1.2 Motivation
Currently in use for communication in combat situations is radio frequency
communication. This method of communication is often unreliable and insecure, as anyone with
the correct frequency would be able to listen in to a conversation. With free space optical
communication the connection is much more secure, in that only those within a direct line of the
beam would be able to intercept the packets being sent. The photodetector or photomultiplier
tube that intercepts the beam must be tuned to the correct wavelength in order to detect the light.
The optical communication system also allows much more than voice transmissions, as data of
all sorts can be sent to accompany any message.
2. Project Description and Goals
The line of sight portion of the Optical Voice and Data Toolkit involved the creation of a
transmitter, made up of a 405nm blue laser that transmits voice and data to a receiver. Originally
an eye safe and covert light was to be used, but the only available source we had was an
ultraviolet LED. This LED did not have enough power to transmit long distances and was thus
dropped. High power lasers that are both eye safe and covert are very expensive and thus out of
our given budget. The laser transmitter and receiver were connected to an Altera DE2 board
which acts as a Digital Signal Processor. The transmission board converts the analog voice into a
digital stream while the receiving board converts the digital stream to analog for playback. Data
Optical Voice and Data (ECE4007L03)
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is similarly transferred through the first board and the laser but the reception program on the
other end was not completed because of the time constraints of the semester.
Although the system works as a proof of concept demonstration, there is a lot of
extraneous noise and feedback present which needs to be filtered out. Beyond that, the voice
portion took longer than expected and data transmission was accomplished with reception
needing to be done in the future. The same goes with the laser, although a normal blue laser was
used, with a higher budget, the proper eye safe and covert laser can be purchased and the same
results accomplished.
The final system does the following:

Allows for voice and data transmission between two points

Laser and lens systems allows for 20 meter transmission distance

Final cost of $3148.00 of required parts and equipment

405nm blue laser used
3. Technical Specifications
The following specifications are divided up into the different components of the project
with the proposed and actual specifications in respective columns. Each section has certain
requirements that must be met in order for the full system to succeed. The laser transmitter must
have a certain wavelength which the client has required to be eye safe and covert. The
accompanying photodetector must be able to absorb light at this wavelength which is its spectral
response.
Data transfer speeds must be fast in order to satisfy the clients need for up-to-date
information in real time. Voice must be played back unaltered with little to no lag and thus must
Optical Voice and Data (ECE4007L03)
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have the specified frequency of sampling and latency as well as standard encoding. Data and
voice input/output will allow an easy to use interface with little explanation in use.
Finally the general specification as the end are those that will ensure a successful
environmental and user integration. The range of communication must allow users to be far
enough away to allow such optical communication necessary yet not too far to make it
impossible. The Altera DE2 board user interface allows for easy use with little complication.
Table 1. Project Specifications.
Laser
Transmitter
Photomultiplier
Tube
Data
Input/output
General
Specifications
Light
Wavelength
Output Power
Spectral
Response
Responsitivity
Avg. Data
Transfer
Min. Voice
Latency
Voice Sampling
Voice Encoding
Audio Input
Audio Output
Data Input
Range
User Interface
Proposed
Eye safe/Covert
(1550nm)
6 mW
Actual
240 mW pulsed
800 – 1700 nm
165 – 650 nm
0.9 A/W
--
2 Mbps – 25 Mbps
~45 Mbps
1 second
0 seconds
8 kHz
G.711 PCM
1/8” mono jack
1/8” mono jack
USB
20 – 500 meters
Altera DE2 Board
pushbuttons,
dipswitches and LCD
Screen
8 kHz
G.711 PCM
1/8” mono jack
1/8” mono jack
USB
20 meters
Blue (405nm)
Altera DE2 Board
dipswitches and
LEDs
4. Design Approach and Details
4.1. Design Details
The Optical Voice and Toolkit consists of multiple parts as shown in Figure 1. A
headset/microphone is used to transmit analog voice data to the DSP board. The headset is
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directly connected to the DSP board, in this case an Altera DE2 board, via a standard 1/8”
(3.5mm) audio jack. Along with this external voice input, a USB connection is used to transfer
data to the DE2 board as well. The DE2 board has multiple dip switches and push buttons as well
as input/output ports for our various needs. The voice is encoded using the ITU-G.711 PCM
standard and digitized using the Wolfson WM8731 audio codec on the board. The flowchart in
Figure 2 shows the functional diagram of the code which accomplishes this task. The digitized
voice and data is then sent out of pin GPIO1_3 of the DE2 board through a laser driver
consisting of 4 NAND gates in parallel as shown in Figure 3. This then converts the TTL/CMOS
signal from the board to the required current of 40mA to drive the laser transmitter. The laser
transmitter pulses the 405nm blue laser to the receiving lens system 20 meters away in direct line
of sight.
On the receiving end of the design, a 3x3 inch lens with an effective diameter of 2.5
inches focuses the incoming beam onto the photomultiplier tube (PMT) allowing the maximum
amount of photon detection allowing for the greatest current. The current from the PMT is
converted to a voltage and amplified with the PMT control box and then further amplified to
about 4.6V, shown in Figure 4, to be read by pin GPIO1_3 of a second DE2 board. This board
then decodes the voice message and converts the digital signals back to analog allowing for
playback through a set of speakers. The data is ready to be sent through the laser and is being
transmit when looked at through an oscilloscope but the program to receive and decode the
packets was not able to be created in the time constraints of the semester. The entire process is
again outlined by the flowchart in Figure 1.
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Figure 1. Design Flowchart.
Figure 2. Encoder functional
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Figure 3. Transmission Circuit.
Figure 4. Receiving Circuit.
Optical Voice and Data (ECE4007L03)
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4.2. Codes and Standards
Inputs/Outputs
In order to make the design process simple certain codes and standards will be used.
Standard 1/8” audio jacks will be used as both a headset input and speaker output on the Altera
DE2 boards. This will allow for standard plug and play equipment to be used as well as making
use of I/O ports made available on the boards.
Standard USB 2.0 will be used to transfer data to the DE2 board. The Altera board has a
built in USB 2.0 port, allowing for transfer speeds up to 480 Mbits/s, according to the USB 2.0
specs.
Voice
The standard encoding for audio signals incorporating just voice is the ITU-G.711 Pulse
Code Modulation standard. This is the long existing standard which samples the data at 8000
samples per second allowing for minimal data loss involved [7].
5. Schedule, Tasks, and Milestones
Each team member worked on every aspect of the project with specific tasks being
assigned to certain members. Table 2 shows the schedule of the project with each task, start date,
end date, duration, and the team member who head up that particular task. These responsibilities
were assigned based on the strengths and expertise of each group member to achieve the best
efficiency in accomplishing each task. The milestones of the project are shown in italics. These
milestones are the most important aspects of the project and each of these tasks must be
accomplished in order to achieve and overall success in the end. These milestones were
accomplished and the overall project was a success. The start of the project was on August 18,
Optical Voice and Data (ECE4007L03)
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2009 and was completed on December 10, 2009. The complete Gant chart of the project can be
found in Appendix B.
Table 2. Project Schedule.
Task Name
Project Decision
Technical Reports
Written Proposal
Product Decision and Purchase
Short Range Detection
Encode and Decode Voice Data
Long Range Transmission
Draft Project Summary
Project Summary
Demonstration
Final Presentation
Project Report
Start
End
Duration
Responsibility
Aug 18
Aug 18
Sep 2
Sep 8
Sep 25
Sep 16
Oct 16
Sep 16
Sep 30
Nov 20
Nov 20
Nov 20
Sep 2
Sep 2
Sep 16
Sep 25
Oct 16
Dec 7
Nov 30
Sep 30
Dec 4
Dec 7
Dec 7
Dec 10
15 Days
14 Days
14 Days
17 Days
21 Days
82 Days
45 Days
14 Days
65 Days
17 Days
17 Days
20 Days
Team
Individual
Gandhi
Team
Team
Grubl
Hunold
Gandhi
Gandhi
Team
Team
Gandhi
6. Results and Acceptance Testing
With the completion of the prototype the testing phase of the project began. The main
goals of this phase were to determine if the original proposed objectives could be were met. First
the transmission and receiving programs were downloaded onto each of the DE2 boards. Once
this was accomplished, the transmission board is set to either voice or data transmission
Figure 5. DE2 Board transmission switches.
Optical Voice and Data (ECE4007L03)
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depending on what the user desires using the Altera DE2 board interface as shown in Figure 5.
Using SW2, voice is set to be sent from one board to the other using the optical network.
The user talks into the microphone which is connected to the 1/8” mono jack input and voice is
output through the 1/8” mono jack on the second board. Using the PCM coding format the speed
at which the voice is transferred was determined to be the sample rate multiplied by the number
of bits in the stream. Using this formula the speed is determined to be 8000 * 16 = 128kbps.
Unfortunately there was much noise and data loss between the two boards and therefore the
playback of the voice was less than ideal. This was determined to have occurred because of a
lack of synchronization between the two boards. This was temporarily fixed by using only one
board. Data was still transferred from output pin to input pin using the laser and photomultiplier
tube, but both the decoding and encoding are done on the same board eliminating
synchronization issues. This was how the technology was demonstrated.
To transmit data, the user switches on SW1, as outlined in Figure 5. Data transmission
was set up on the first board but there was not enough time to complete the reception of the data
on the second board. To show the data being read and set up, LEDs R0 – R15 show the 4 digits
that can be sent via binary. This transmission waveform was also detected using an oscilloscope.
The data is written and read from memory using the Altera DE2 Control Panel program that
came standard with the DE2 board software packages.
Finally even though the voice had much data loss and there was extraneous noise using
two boards, the range requirement of the project was met. The same waveform being detected
from the first board was also detected on the second board 20 meters away. This was confirmed
with a scope capture as shown in Figure 6, and a range finder which showed us the total range of
Optical Voice and Data (ECE4007L03)
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the proof-of-concept design. Figure 7 shows parts of the full set up of the entire system, both the
boards and the optical setup used.
Figure 6. Voice transmission waveform.
Figure 7. Optical setup (right) and DE2 Board setup (left).
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7. Budget and Cost Analysis
On of the biggest issue of this project was the fact that there was not enough funding to
get the high end parts and equipment required. Because of this constraint, parts were obtained via
the senior design laboratory supplies and the Georgia Tech Research Institute through the project
advisors. The total cost of the parts themselves was found to be approximately $3148.00. This
price does not include labor costs or any marketing costs as this project was simply a proof of
concept design. For marketing purposes, more money will be required to modularize the
technology to something acceptable for use in the field. Out of our given senior design budget of
approximately $400, the team only spent a total of $150.00 on the lens system needed for long
distance communication and distance. The complete chart of prices as well as where each part
was obtained is given in Table 3.
Table 3. Transmitter Section Price List.
Component
Price
Microphone/headset
$20.00
Altera DE2 Board
$269.00 (x2)
Laser
$60.00 (x2)
PMT Control Box
$300.00
PMT
$2000.00
Lens System
$150.00
Speakers
$20.00
Total
$3148.00
Purchasing
Senior Design
Senior Design
Senior Design
Advisor
Advisor
Purchased
Senior Design
$150.00
8. Conclusions and Future Work
Currently the project has been completed and the goals originally proposed have been
met for the most part. The major portions of the design, using a laser to transmit data and voice
and obtaining a distance of at least 20 meters have been accomplished. The team expected to be
able to clean up the voice transmission a little more but with time constraints and budget issues
Optical Voice and Data (ECE4007L03)
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this was not possible. Given the resources available to the group, a solid foundation for free
space optical communication has been created for future groups to build upon.
The major changes that need to be done to create improvements on the system include
cleaning up the synchronization and data loss issue, creating a more modular design to be
implemented on existing military equipment, and having the entire system powered via batteries.
With these changes and improvements, the system would be more in line with the original
project requirements from the client.
In order to clean up the voice and eliminate the data loss, a Universal Asynchronous
Receiver/Transmitter (UART) needs to be implemented. This will allow the packets of data to be
framed with a specific starting and stopping point. On the receiving end, the packets can be
reconstructed accurately without the excess noise and loss. Along with this, the entire system
needs to be made smaller, allowing for it to be attached to existing military equipment such as
rifle scopes and binoculars. Creating these modular parts will require the system to be powered
by batteries, since the largest voltage needed for the current system is only about 9V, making the
entire system battery powered is very feasible for future groups.
Finally, with those modifications made, more of the original project can be attempted.
The non line-of-sight portion of data transfer can be looked into as well as creating a base relay
station to intercept the data and voice in a central area for easy access. The important part of any
future work is to do the research required on the technology and implementation of the
technology and to manage the given time wisely to only tackle a small portion of each addition
rather than all of the additions at once.
A complete list of possible future additions is as follows:

Create the UART system to eliminate data loss
Optical Voice and Data (ECE4007L03)
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
Downscale the prototype in a modular design to attach to existing military
equipment

Make the entire system battery powered

Attempt non line-of-sight transmission of voice and data

Create a central relay station to intercept all incoming data
Optical Voice and Data (ECE4007L03)
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9. References
[1] Combating Terrorism Technology Support Office, "Broad Agency Announcement (BAA),"
Combating Terrorism Technology Support Office, 2007.
[2] Mitsubishi Laser Diodes, "ML9xx45 Series," Datasheet 2004.
[3] fSONA. (2009) fSONA Optical Wireless. [Online]. http://www.fsona.com/index.php
[4] "Free-space-optics vendors find new markets in traditional places," Laser Focus World, vol.
41, no. 8, August 2005.
[5] Dr. Stephen Pappert. (2005, April) Defense Advanced Research Projects Agency (DARPA).
[Online]. http://www.darpa.mil/mto/solicitations/baa05-36/
[6] ThorLabs, "FGA04 InGaAs Photodiode," Datasheet 2000.
[7] International Telecommunication Union. (1993) International Telecommunication Union.
[Online]. http://www.itu.int/rec/dologin_pub.asp?lang=e&id=T-REC-G.711-198811-I!PDFE&type=items
[8] Inc. Edmund Optics. (2009) Edmund Optics Worldwide. [Online].
http://www.edmundoptics.com/
[9] ThorLabs. (2009) ThorLabs. [Online].
http://www.thorlabs.com/Navigation.cfm?Guide_ID=36
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Appendix A – Full Project Description
Original Project Description R2268
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W91CRB-07-T-0155 BAA Package
August 3, 2007
the Aqua-Ram, and the Scalable Improvised Device Defeat. The system shall facilitate
remote delivery, rapid deployment, and application of these tools on any terrain, and must
be capable of withstanding extreme environmental conditions and rough handling during
transport and operations. Typical operating environments range from desert to artic
conditions. The system must travel in a “neutral position” and adjust to the position
required for proper placement and attachment of the tool. Height adjustment to properly
position and secure disruption tools weighing up to 600 pounds against different sized
threat vehicles that range from a standard sedan up to a tractor-trailer type vehicle to
include fuel tanks, sewage trucks, water tankers, and sea-land containers is required. The
adjustment of the system must be made quickly and easily without the use of special
tools, and must be configured to allow for easy attachment to and release from current
EOD robotic platforms. The system must be compatible with the Foster-Miller Talon
(IIIB, MTRS, and GEN IV); the Remotec ANDROS family of robots (including the
F6A, the Remote Ordnance Neutralization System, the MK V-A1, the Mini-ANDROS II,
the HD-1,
and the Wolverine); the iRobot Warrior and Packbot EOD; and the Allen-Vanguard
Vanguard MK II platform; however, solutions focusing on the development of a self
propelled/self loading system will be considered. Systems may use robot power or
provide its own power, and must have a release and braking mechanism for manual and
remote disconnect. The proposed system must be transportable in a typical bomb squad
response vehicle and not require special handling equipment. The system shall be
constructed of a material that provides a reduced fragmentation hazard in the event of a
detonation. Affordability to the end user community shall be a prime factor in system
design. System developer must either establish a suitable teaming/partnership or be able
to independently provide all aspects of developing, fabricating, testing, manufacturing,
and commercializing the end item.
5.6. Investigative Support and Forensics -(IS)
Mission: Identify, prioritize, and execute projects that satisfy interagency requirements for
criminal investigation, law enforcement, and forensic science technology applications in errorism
related cases.
R2337 Geolocation Using Image Analysis
Design and develop a prototype for an automated hardware/software system that identifies
physical geographic locations from video and image data. Use forensic video,
photogrammetry, and advanced geospatial analysis techniques to deduce sites depicted in
terrorists' videos. The system should be able to enhance the quality of the video and
combine images from multiple video inputs, if available. Datasets must be acquired to
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form the basis for the methodology. Produce a report showing the image from the
questioned video compared to that in the known dataset as well as the name and
coordinates of the resultant location. The output of the video image processing and
evaluation must occur in a timely manner.
5.7. Tactical Operations Support (TOS)
Mission: Identify, prioritize, and execute projects that satisfy DoD and interagency user
requirements for equipment and systems to support specialized force offensive operations
directed against terrorist activities and groups. The use of nonsensitive prototype hardware for
state and local law enforcement agencies is considered for transition and commercialization.
R2268 Optical Voice and Data Communications Toolkit for Tactical Forces (Civilian
Law Enforcement)
Develop a set of interoperable optical voice and data communications devices for use by
tactical forces in urban and suburban environments. The system could be used in rural,
wilderness, or maritime environments as part of any tactical operation. The system should
provide stationary teams with an alternative to standard radio-frequency (RF)
communications that is easily emplaced, secure, and provides high-bandwidth
connectivity, yet has a low probability of detection/intercept when compared to standard
RF systems and is relatively inexpensive. The intent of this project is to build and refine
various components that will comprise the tactical toolkit. Affordability of the toolkit is a
consideration with a target of less than $30K per toolkit.
The system shall be eye-safe and provide both data and voice communications across a
minimum distance of 3 kilometers (threshold) with a goal of 10 kilometers or more
(desired/objective).
-Data: minimum 2Mbps (threshold) with higher rate desired (25Mbps is objective).
-Voice: 32 Kbps simultaneous with data (threshold).
-Communications links must be securable via application of Advanced Encryption
Standard (AES) compliant techniques.
-Components must accept input from, and provide output to, standard video, audio,
and data systems including, but not limited to laptops and PDA.
-Components must be constructed to withstand rugged operating conditions
(threshold), MILSPEC 810F is desired (objective).
-Components must operate from rechargeable DC power and accept power inputs
ranging from 7-36 volts.
-The system shall function from a stationary mode as a minimum; a system that is
also capable of operating while moving is desired.
The toolkit will be modular in design and consist of multiple interoperable components.
As a minimum, the toolkit will consist of the following components:
-Binocular Appliqué. A device that attaches to standard binoculars, but does not
interfere with standard binocular functions.
-Scope Appliqué. A device that attaches to standard spotting/rifle scopes, but does
not interfere with standard scope functions.
Optical Voice and Data (ECE4007L03)
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-Hand-held Unit. A device that is similar in appearance to a flashlight and can
receive and transmit through integral optics.
-Relay Station. System for connecting devices when line-of-sight is not possible
for a minimum of two devices, but four or more devices simultaneously are desired. Once
emplaced, this relay station must be capable of sustained operations from internal power
source for at least 30 hours (96 hours is desired / objective) of continuous operation. The
relay station shall include an optional user-installable encryption module.
-Wearable Unit. A device worn by the operator, yet is difficult for a casual
observer to detect, to transmit voice/data. A minimum range of 600 meters with
simultaneous voice / receive capability is desired.
-Miniature Device(s). A miniature, light-weight device that attaches to various
unattended surveillance sensors (such as, cameras, microphones or other sensors),
transmits collected voice/data, and receives control signals for the sensor. The device must
be capable of sustained operations from internal power source for 30 hours with 96 hours
desired. The minimum range is 600 meters and includes an optional user-installable
encryption module.
-Mounting stands/tripods and storage/transport cases.
Components or component features that are desired include:
-On-the-Move Tracking. An automatic, self-correcting/aligning capability for
receive/transmit devices that is adaptable to ground or air vehicles.
-Integral Binocular and Scope. A field binocular or spotting scope with the
communication elements installed as integral components (vice an appliqué). These
components will be included in the toolkit based on feasibility and affordability.
R2319 Within Field-of-View Image/Data Projector for Snipers (Scope Mounted)
Develop a projector that attaches to existing sniper scopes and provides the sniper with an
externally generated “heads-up display” within the view of the scope. This system will
enable the depiction of graphics over “live action” as well as in the margins outside the
scope field-of-view. Its primary purpose is to display a continuously updated aim point
that accounts for shot variables -including range to the target, ammunition being fired and
crosswinds – generated by an external device. Its secondary purpose is to display
externally-generated sniper-relevant data or imagery on the periphery of the scope’s fieldof-view. The objective of this project is to build and refine field-testable prototypes.
This projector must attach to existing sniper rifle scopes, cause minimal
relocation/adjustment to
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Appendix B – Gant Chart
See Gant Chart Below.
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