NASA/TM⎯2005-212565

EMERGING COMMUNICATION 

TECHNOLOGIES (ECT) 

PHASE 4 REPORT 

Gary L. Bastin, Ph.D. 

ASRC Aerospace Corporation, John F. Kennedy Space Center, Florida 

William G. Harris, PE 

ASRC Aerospace Corporation, John F. Kennedy Space Center, Florida 

José A. Marín 

ASRC Aerospace Corporation, John F. Kennedy Space Center, Florida 

Richard A. Nelson 

NASA, YA-D7, John F. Kennedy Space Center, Florida 

September 2005 
 

The NASA STI Program Office . . . in Profile 

Since its founding, NASA has been dedicated to 

the advancement of aeronautics and space 

science. The NASA Scientific and Technical 

Information (STI) Program Office plays a key 

part in helping NASA maintain this important 

role. 

The NASA STI Program Office is operated by 

Langley Research Center, the lead center for 

NASA’s scientific and technical information. 

The NASA STI Program Office provides access 

to the NASA STI Database, the largest 

collection of aeronautical and space science STI 

in the world. The Program Office is also 

NASA’s institutional mechanism for 

disseminating the results of its research and 

development activities. These results are 

published by NASA in the NASA STI Report 

Series, which includes the following report 

types: 

• TECHNICAL PUBLICATION. Reports of 

completed research or a major significant 

phase of research that present the results of 

NASA programs and include extensive data 

or theoretical analysis. Includes 

compilations of significant scientific and 

technical data and information deemed to be 

of continuing reference value. NASA’s 

counterpart of peer-reviewed formal 

professional papers but has less stringent 

limitations on manuscript length and extent 

of graphic presentations. 

• TECHNICAL MEMORANDUM. Scientific 

and technical findings that are preliminary 

or of specialized interest, e.g., quick release 

reports, working papers, and bibliographies 

that contain minimal annotation. Does not 

contain extensive analysis. 

• CONTRACTOR REPORT. Scientific and 

technical findings by NASA-sponsored 

contractors and grantees. 

• CONFERENCE PUBLICATION. Collected 

papers from scientific and technical 

conferences, symposia, seminars, or other 

meetings sponsored or cosponsored by 

NASA. 

• SPECIAL PUBLICATION. Scientific, 

technical, or historical information from 

NASA programs, projects, and mission, 

often concerned with subjects having 

substantial public interest. 

• TECHNICAL TRANSLATION. 

 English-language translations of foreign 

scientific and technical material pertinent to 

NASA’s mission. 

Specialized services that complement the STI 

Program Office’s diverse offerings include 

creating custom thesauri, building customized 

databases, organizing and publishing research 

results . . . even providing videos. 

For more information about the NASA STI 

Program Office, see the following: 

• Access the NASA STI Program Home Page 

at http://www.sti.nasa.gov

• E-mail your question via the Internet to 

help@sti.nasa.gov 

• Fax your question to the NASA STI Help 

Desk at (301) 621-0134 

• Telephone the NASA STI Help Desk at 

(301) 621-0390 

• Write to: 

 NASA STI Help Desk 

 NASA Center for AeroSpace 

Information 

 7121 Standard Drive 

 Hanover, MD 21076-1320 
 

NASA/TM⎯2005-212565

EMERGING COMMUNICATION 

TECHNOLOGIES (ECT) 

PHASE 4 REPORT 

Gary L. Bastin, Ph.D. 

ASRC Aerospace Corporation, John F. Kennedy Space Center, Florida 

William G. Harris, PE 

ASRC Aerospace Corporation, John F. Kennedy Space Center, Florida 

José A. Marín 

ASRC Aerospace Corporation, John F. Kennedy Space Center, Florida 

Richard A. Nelson 

NASA, YA-D7, John F. Kennedy Space Center, Florida 

National Aeronautics and 

Space Administration 

John F. Kennedy Space Center, Florida 32899-0001 

September 2005 
 

Acknowledgments

.Although there is always the risk of inadvertently forgetting someone, the ECT team nonetheless wishes to 

acknowledge especially the assistance and guidance provided by the following individuals, listed 

alphabetically. Without the continued support of these supporters who believed in the value of this project, 

this project could not have accomplished all its goals. 

Name Organization

Dr. Larry Andrews University of Central Florida 

Michael Borbath Harris Corporation 

Dr. Geoffrey Burdge Harris Corporation 

Temel Erdogan ASRC Aerospace Corporation 

Bobby Ferrell NASA KSC 

James Kennedy NASA KSC 

Jennifer Murray NASA KSC 

Dr. Ron Phillips University of Central Florida 

Ennis Shelton NASA KSC 

Art Shutt ASRC Aerospace Corporation 

Ed Taff NASA KSC 

Frida Störmqvist Vetelino University of Central Florida Graduate Student 

The help provided by Mr. Ed Taff, NASA Shuttle Landing Facility (SLF) Manager, in coordinating the use 

of the SLF runway as a laser test range, while not impacting Shuttle Training Activities (STA) required by 

astronaut crews training for Return to Flight (RTF) is gratefully acknowledged. Mr. James Kennedy, 

Center Director of the John F. Kennedy Space Center, is gratefully acknowledged in approving our nonstandard use of the SLF despite the schedule pressures of RTF. The addressing of safety issues associated 

with our unusual use of the SLF could not have occurred without the able assistance of Mr. Ennis Shelton, 

of NASA KSC Health Physics, and of Mr. Arthur Shutt, Safety Engineer of the University-affiliated 

Spaceport Technology Development Contract (USTDC.) Their continued assistance through the lengthy 

period of collecting data is gratefully acknowledged. The support of Harris Corporation, in supplying 

personnel and test equipment to enable the collection of real-time scintillometer data and weather data, is 

gratefully acknowledged. Likewise, the support of the Florida Space Institute, and of the University of 

Central Florida, in sharing research equipment and providing assistance from Graduate Students is 

gratefully acknowledged. The technical support of fSONA Communications Corporation, Richmond, BC, 

Canada, in answering technical questions and supporting conference calls, is gratefully acknowledged 

Available from: 

NASA Center for AeroSpace Information National Technical Information Service 

7121 Standard Drive 5285 Port Royal Road 

Hanover, MD 21076-1320 Springfield, VA 22161 
ECT – Phase 4 

TABLE OF CONTENTS 

No. Description Page 

1.0 Introduction............................................................................................... 1

1.1 Background................................................................................................. 1 

1.2 Objectives ................................................................................................... 2 

1.3 Scope........................................................................................................... 2 

1.4 ARTWG / ASTWG..................................................................................... 2 

2.0 Free Space Optics...................................................................................... 5

2.1 Background................................................................................................. 5 

2.2 Basic FSO Theory....................................................................................... 6 

2.3 Test Description.......................................................................................... 7 

2.4 Test Objectives ........................................................................................... 8 

2.5 Test Locations & Setups............................................................................. 8 

2.5.1 SpaceHab Optical Laboratory................................................................... 11 

2.5.2 EDL East Parking Lot............................................................................... 14 

2.5.3 Schwartz Road Test Setup ........................................................................ 16 

2.5.4 Shuttle Landing Facility............................................................................ 18 

2.6 Test Equipment And Software.................................................................. 22 

2.6.1 SONAbeam 622-M ................................................................................... 22 

2.6.2 AirFiber 5800............................................................................................ 28 

2.6.3 SmartBits................................................................................................... 30 

2.6.4 Pattern Generators..................................................................................... 30 

2.6.5 Error Detectors.......................................................................................... 31 

2.6.6 Receiver .................................................................................................... 31 

2.6.7 Clock and Data Recovery (CDR) ............................................................. 31 

2.6.8 Weather Station......................................................................................... 31 

2.6.9 Scintillation............................................................................................... 31 

2.6.10 SONAbeam Terminal Controller Software .............................................. 33 

2.6.11 SmartApplications .................................................................................... 33 

2.7 Test Results............................................................................................... 33 

2.7.1 Prior Art and Historical Rationale for Testing Methodology................... 33 

2.7.2 Testing Methodology................................................................................ 35 

2.7.3 Instrument Operation ................................................................................ 36 

2.7.4 Theoretical Equations............................................................................... 38 

2.7.5 Detailed Results........................................................................................ 41 

2.7.6 Conclusions and Recommendations For Further Research ...................... 46 

3.0 EXTENDED RANGE WIFI .................................................................. 49

3.1 Background............................................................................................... 49 

3.2 Basic E-R Wi-Fi Theory ........................................................................... 49 

3.3 Choice Of E-R Wi-Fi For Testing ............................................................ 50 

3.4 Test Description........................................................................................ 51 

3.5 Test Objectives ......................................................................................... 51 

3.6 Test Setup ................................................................................................. 51 

3.6.1 Schwartz Road Test Setup ........................................................................ 52 

 iii
ECT – Phase 4 

3.6.2 Shuttle Landing Facility (SLF) Test Setup............................................... 54 

3.7 Test Equipment And Software.................................................................. 54 

3.7.1 DragonWave AirPair 100 ......................................................................... 54 

3.7.2 Laptop ....................................................................................................... 59 

3.7.3 DragonWave AirPair 100 Controller Software ........................................ 59 

3.7.4 DragonWave Link Tool ............................................................................ 62 

3.7.5 Throughput Testing................................................................................... 63 

3.8 Test Results............................................................................................... 64 

3.8.1 General...................................................................................................... 64 

3.8.2 Results Summary ...................................................................................... 65 

3.9 E-R Wi-Fi Security Concerns................................................................... 68 

3.10 E-R Wi-Fi Summary And Recommendations .......................................... 68 

4.0 Ultra Wide Band ..................................................................................... 71

4.1 Introduction............................................................................................... 71 

4.2 Background............................................................................................... 71 

4.3 UWB Waveform INVESTIGATION UPDATE....................................... 72 

4.4 Standards updates ..................................................................................... 73 

4.5 UWB antenna updates............................................................................... 73 

4.6 Summary of Results.................................................................................. 74 

4.7 Recommendations for Future Research.................................................... 74 

5.0 ECT Summary Recommendations For Continued Research............. 75

APPENDIX A: Acronyms & Definitions.................................................................. 77

APPENDIX B: Optical BER Equations For OOK.................................................. 81

APPENDIX C: Extended Range Wi-Fi Test Results............................................... 83

 iv
ECT – Phase 4 

LIST OF FIGURES 

No. Description Page 

Figure 1-1 ARTWG National Development Strategy ...................................................4 

Figure 2-1 Typical Link-Verification Setup Using SmartBits ...................................10 

Figure 2-2 Typical BER Test Setup ...........................................................................10 

Figure 2-3 SpaceHab Optical Lab Setup ....................................................................12 

Figure 2-4 fSONA Units Being Tested In The SpaceHab Optical Lab......................12 

Figure 2-5 Beam Measurements Between OTU #1 & OTU #2 .................................13 

Figure 2-6 EDL Parking Lot.......................................................................................14 

Figure 2-7 OTU-1 in EDL Parking Lot ......................................................................15 

Figure 2-8 OTU-2 At South End of EDL Parking Lot ...............................................15 

Figure 2-9 AirFiber #1 On Trailer #1 in EDL Parking Lot........................................16 

Figure 2-10 OTU #2 Parked In The Bend On The West End of Schwartz Rd............17 

Figure 2-11 OTU #1 Positioned @ 1 Km On Schwartz Rd........................................17 

Figure 2-12 SLF Viewed From North ........................................................................18 

Figure 2-13 Typical Aircraft Traffic at SLF...............................................................19 

Figure 2-14 fSONA #2 on SLF Centerline.................................................................19 

Figure 2-15 fSONA #1 With SmartBits, Laptop & Open Control Panel ...................20 

Figure 2-16 SLF South Setup With fSONA #1, FSI Trailer, and Scintillometer.......20 

Figure 2-17 South SLF Setup With Van and Trailer..................................................22 

Figure 2-18 Front of SONAbeam 622-M OTU .........................................................23 

Figure 2-19 SONAbeam Junction Box Open ............................................................25 

Figure 2-20 Pole Mount with OTU, Connection Box & Power Supply Box ............25 

Figure 2-21 Aperture Adapter and Mask...................................................................26 

Figure 2-22 Aperture Adapter and Mask...................................................................27 

Figure 2-23 AirFiber 5800 With Fiberglass Shroud Removed..................................28 

Figure 2-24 Field Testing with the SmartBits & a Laptop ........................................30 

Figure 2-25 Wx Station and Scintillometer Rx on SLF.............................................32 

Figure 2-26 Transmit Portion of Scintec Scintillometer............................................32 

Figure 2-27 Measured Average Cn

2

 Values...............................................................36 

Figure 2-28 Values of Inner Scale from 1-min. Avg. Wind Speed ...........................37 

Figure 2-29 1-min. Avg. BER Vs. SNR ....................................................................42 

Figure 2-30 5-min. Avg. BER Vs. SNR ....................................................................43 

Figure 2-31 BER & Error Count Vs. Time of Day & Aperature Dia........................44 

Figure 2-32 BER Vs. Time of Day @ 1.0 & 1.25 Aperture Dia. ..............................45 

Figure 2-33 BER & Cn

2

 Values Vs. Time of Day @ 1.0 & 1.25 Aperture Dia.........46 

Figure 3-1 AirPair 100 On Trailer #2 At West End Of Schwartz Rd..........................53 

Figure 3-2 AirPair 100 On Trailer #1 At East End Of Schwartz Rd...........................53 

Figure 3-3 Modified AirPair 100 Radio with 30cm Antenna & Added Riflescope....55 

Figure 3-4 AirPair 100 Outdoor Modem.....................................................................56 

Figure 3-5 Power + Ethernet Cable .............................................................................58 

Figure 3-6 Pole Mount with AirPair 100 Modem, Radio, and Antenna .....................58 

Figure 3-7 Laptop connected to the AirPair 100 Modem............................................60 

 v
ECT – Phase 4 

Figure 3-8 CLI screen capture (Laptop)......................................................................61 

Figure 3-9 Web Interface – General Radio Information Page.....................................61 

Figure 3-10 LinkTool utility..........................................................................................63 

Figure 3-11 Throughput Versus Distance .....................................................................67 

Figure 3-12 Average Throughput versus Distance........................................................68 

 vi
ECT – Phase 4 

LIST OF TABLES 

No. Description Page 

Table 2-1 FSO Industry Comparisons for FY05..........................................................6 

Table 2-2 FSO Test Locations ...................................................................................11 

Table 2-3 SONAbeam 622-M Specifications ............................................................23 

Table 2-4 AirFiber 5800 Specifications.....................................................................29 

Table 2-5 Summary of Test Locations & Objectives.................................................33 

Table 3-1 Test Locations............................................................................................52 

Table 3-2 AirPair 100 Specifications.........................................................................57 

Table 3-3 AirPair 100 Test Configuration Parameters...............................................59 

Table 3-4 Optimum RSL Values Vs Distances..........................................................62 

Table 3-5 Optimum Parameters .................................................................................62 

Table 3-6 Summary of Test Locations & Objectives.................................................65 

 vii
ECT – Phase 4 

 viii
ECT – Phase 4 

Executive Summary 

________________________________________________________________________ 

The National Aeronautics and Space Administration (NASA) is investigating alternative 

approaches, technologies, and communication network architectures to facilitate building 

future Spaceports, building on the communications capabilities that already exist. These 

investigations support the development of communication networks for use with the 

Crew Exploration Vehicle (CEV), as well as other crafts presently under development or 

under consideration in the Government, academic, and private sectors. Forming part of 

the associated Ground Support Equipment (GSE) that will be necessary to prepare and 

launch these space crafts, the communication technology resulting from these 

investigations will also provide a national centralized R&D forum for next-generation 

Spaceport and Range technology development. Together, these sectors share the 

common goal of changing the historic risk/reward equation for access to space, especially 

with regards to communications networks, with the intent to: 

• Dramatically reduce launch cost 

• Greatly improve launch system reliability 

• Significantly reduce crew risk 

During FY05, ECT Phase 4 accomplished the following major milestones: 

• Performed FSO scintillation and aperture averaging testing on the Shuttle 

Landing Facility (SLF) Runway, with the runway used as a giant laser test range 

• Validated published theoretical equations for predicting the performance 

enhancements possible through increasing receiver apertures to mitigate the 

effects of optical scintillation 

• Wrote and published an SPIE Technical Conference Paper, San Diego (August 

2005) on the use of aperture averaging to mitigate scintillation and improve Bit 

Error Rate (BER) for high data rate Free Space Optical links 

• Supported and encouraged University of Central Florida personnel to utilize data 

through sharing SLF optical test data, which resulted in two additional technical 

conference papers being published at the SPIE in San Diego (August 2005) 

• Trained personnel on extended range WiFi equipment at vendor facility, and 

subsequently performed extended range WiFi testing within the unique Kennedy 

Space Center environment 

• Evaluated and tracked UWB industry developments 

• Identified 3 additional technology topics needing investigation in Phase 5, FY06: 

(WiMAX, second generation UWB, and FSO networking and beam wander 

issues) 

 ix
ECT – Phase 4 

 x
ECT – Phase 4 

 

1.0 INTRODUCTION

1.1 BACKGROUND 

Emerging Communication Technologies is a multi-year task investigating new 

communication technologies with a high probability of utilization and application for 

future ranges and spaceports. 

In year one, the project was called Range Information Systems Management (RISM)1

. 

This project investigated US ranges and documented their missions, capabilities, and 

infrastructures. A part of this investigation was the identification of past historical trends 

in communication technology and the identification of new, emerging technologies which 

might offer improved range communication capabilities in the near future. Three 

emerging communication technologies were identified: Free Space Optics (FSO), 

Extended Range Wireless Ethernet (Wi-Fi), and Ultra Wide Band (UWB). All three of 

these technologies address the first mile / last mile communication solution. 

In year two, specific examples of FSO, UWB and Wi-Fi were purchased and evaluated 

for range application. The FSO hardware purchased and evaluated was an AirFiber 5800 

optical transceiver. This unit includes an auto-tracking feature that maintains optical 

alignment during small movements that normally occur to support structures due to 

diurnal solar heating, winds, and vibration. The units were tested over various distances 

and through various weather conditions. 

The UWB effort in year 2 produced an industry survey, developed a fundamental basic 

UWB mathematical theory, and included testing an Evaluation Kit (EVK) from TimeDomain Corporation. Signal degradation due to range; normal office barriers of 

concrete, metal, partitions, etc.; and the effects of interference from microwave ovens, 

wireless phone, etc., were measured. 

During year 2, two different Wi-Fi systems were purchased and evaluated. One was an 

802.11b base station from Microsoft. The other was an 802.11g system from D-Link. 

The majority of testing for the 802.11b system were signal degradation due to range; 

normal office barriers of concrete, metal, partitions, etc.; and interference from 

microwave ovens, wireless phone, etc. 

During year 3, wide-beam, non-tracking FSO hardware from fSONA was procured and 

evaluated in contrast to the narrow-beam, auto-tracking hardware from AirFiber 

investigated in year 2. Additionally, OFDM-UWB performance limitations were 

investigated through using the same EVK with the addition of new firmware upgrades 

from Time-Domain Corporation as a test bed. Likewise, general industry trends for 

achieving first mile / last mile communications were monitored and incorporated into this 

multi-year ECT activity. 

 

1

 Acronyms and Definitions are provided in Appendix A. 

1
ECT – Phase 4 

 

During year 4, the current year, extensive investigations into FSO, Wi-Fi, and UWB 

technologies continued. Extended-Range (E-R) WiFi technology investigation and 

evaluation was added to the project. Original plans were to investigation performance 

impacts due to multiple FSO wide-beam systems operating in close proximity; however, 

budget constraints and the delayed receipt of funds prevented purchasing a second FSO 

system. With only one wide beam FSO system available, planned FSO scintillation 

testing was accelerated through joining the University of Central Florida, Florida Space 

Institute, Technical University of Catalonia (Spain), and Harris Corporation in 

investigating aperture averaging and scintillation effects on Bit-Error-Rate. Jointly 

conducted testing and theoretical development resulted in three technical papers that 

were presented in August at the San Diego SPIE 2005 Conference. The data for these 

papers were based on multiple FSO tests conducted on the Shuttle Landing Facility 

(SLF) runway. E-R WiFi investigations centered around a Dragonwave COTS system 

procured and then tested over various distances around Kennedy Space Center. UWB 

activities during year four were limited to monitoring developments within the industry, 

commencing a study of UWB waveforms optimized for efficiency, and waiting for new 

evaluation kits to be released. Likewise, general industry trends for achieving first mile / 

last mile communications were monitored and incorporated into this multi-year ECT 

activity. 

 

1.2 OBJECTIVES 

The primary objective for the Emerging Communication Technology (ECT) task is to 

lead the development of a Space Based Range Distributed Subsystem (SBRDS) network 

that provides the concurrent features and growth capabilities necessary for future 

Spaceports and Ranges to interconnect Range assets, Range operations, and Range users 

during launch and recovery events, while focusing primarily on the First Mile/Last Mile 

wireless communication extensions to existing, fixed communication infrastructures. 

1.3 SCOPE 

ECT Phase 4 was limited to the following: 

• Help develop future range and spaceport architectures and needs 

• Investigate FSO scintillation and aperture averaging effects using a fixed 

alignment, wide-beam FSO system 

• Procure, test, and evaluate an Extended Range WiFi system 

• Investigate the capabilities of the Time-Domain upgraded firmware UWB system 

• Commence investigating optimal UWB templates for improving overall system 

power efficiency. 

1.4 ARTWG / ASTWG 

2
ECT – Phase 4 

 

ECT helped develop future range and spaceport architectures and needs through 

participation in the active efforts of: 

• ARTWG (Advanced Range Technology Working Group) 

• ASTWG (Advanced Spaceport Technology Working Group) 

• FIRST (Future Interagency Range & Spaceport Technologies) 

ARTWG is a collaborative NASA/US Air Force/Industry/Academia effort to focus 

interest and investment in Range technologies. It is co-chaired by NASA and the US Air 

Force, and consists of aerospace leaders from industry, academia, and national, state, and 

local governments. ARTWG addresses Range development needs while its companion 

organization ASTWG (Advanced Spaceport Technology Working Group) addresses 

Spaceport development needs. . The initial ARTWG roadmap for future ranges was 

released in March 2004 (Figure 1-1). 

3
ECT – Phase 4 

 

Figure 1-1 ARTWG National Development Strategy 

FIRST is the Future Interagency Range and Spaceport Technologies consortium. FIRST 

is a Tri-Agency consortium consisting of NASA, FAA, and DoD. Its goal is to enable 

joint planning of spaceports and range technologies with each agency controlling its own 

development monies. 

ARTWG, ASTWG and FIRST complement ECT activities and provide opportunities to 

interact with Government, industry, and academic personnel on new developments 

applicable to Ranges and Spaceport of the future. National conferences are held once or 

twice a year. During FY-05, ECT personnel attended the joint ARTWG / ASTWG 

conference in Colorado Springs, CO between January 10th and January 14, 2005. 

4
ECT – Phase 4 

 

2.0 FREE SPACE OPTICS

2.1 BACKGROUND 

Free Space Optics (FSO) was one of the original three First Mile/Last Mile broadband 

wireless access systems identified in the RISM Phase 1 report2. An auto-track system 

from AirFiber was purchased, tested and reported during the ECT Phase 2 activities3

. 

For ECT Phase 3, a fixed-alignment, wide-beam, multiple transmit beam system by 

fSONA was procured and tested. In Phase 4, this system was further utilized to 

investigate scintillation and aperture averaging effects 

FSO is a maturing technology that offers significant advantages over most wireless 

technologies, including higher data rate, and the complete avoidance of any spectrum 

licensing costs. Optical communication systems provide the highest available carrier 

frequencies and thus the fastest data rates possible today. FSO is designed to be a lower 

cost alternative to conventional fiber-optic cable-based communication links4. FSO is 

especially attractive within metropolitan environments where the costs for trenching, 

cable installation, and street repairs can run from $200K to easily over $1M per mile, 

depending on the urban location. 

Although FSO offers the potential of maximum wireless performance, the FSO industry 

continues to be reshuffled. Table 2-1 lists and compares key international FSO players. 

AirFiber, the industry leaders 3 years ago is presently out of business. Terabeam, another 

top FSO company just a few years ago, has sold their assets to Harris Corporation and 

has gone out of the FSO business, focusing instead on wireless opportunities. 

The primary limitations for FSO involve weather and atmospheric effects. Since ground 

links traverse horizontally through the lowest portion of the atmosphere, weather and the 

atmosphere tend to magnify attenuation and scintillation effects. Fog is the primary 

weather concern especially at a 1 mile or less distance. Scintillation effects usually do 

not create serious problems for “First Mile” low to medium data rate links; however, they 

have significant impact on the reliability of higher data rate links and longer links, 

especially. 

 

2

 Range Information Systems Management (RISM) Phase 1 Report, NASA/TM-2004-211523, September 

2002 

3

 Emerging Communication Technologies (ECT) Phase 2 Report, Volume 1, Main Report, NASA/TM2004-211522, September 2003 

4

 http://www.airfiber.com/products/index.htm 

5
ECT – Phase 4 

 

Table 2-1 FSO Industry Comparisons for FY05 

 

Company Tx Auto 

Track

Wave 

Length

Comments 

AirFiber 1 Y 785 Out of business 

Alcatel SA - - - Uses fSONA equipment 

Cablefree Solutions 3 N 780 UK 

Canon Inc. 1 Y 785 USA 

Communication By 

Light GmbH (CBL) 

4 N 870 Germany 

Corning Cable Sys 4 Y 850 USA 

Dominion Lasercom 1 Y 850 USA 

fSona Com 4 N 1550 Canada 

iRLan Ltd. 1 N unk Israel 

LaserBit Com 8 N unk USA. 

LightPointe Comm 4 Y 850 USA. 

LSA Photonics 1 N 785 USA 

Maxima Corp unk unk 10,000 Long wave length infrared; USA 

Mostcom Ltd - - - Same as Sceptre 

Omnilux Inc. 3 unk unk Mesh design, USA 

Sceptre Comm. Ltd. 2 N 850 UK & Russia 

Terabeam Corp. 1 Y 1550 Out of the FSO business, FSO 

Intellectual Property bought by Harris 

Corp. 

TereScope 1 Y 850 USA 

FSO testing during year 4 of the ECT project was conducted using the fSONA 

SONABEAM 622-M transceiver units. Some limited confirmational testing was 

accomplished with the AirFiber units purchased previously, during year two. 

 

2.2 BASIC FSO THEORY 

Free Space Optical (FSO) communication was discussed at length in the previous Phase 1 

RISM report and the ECT Phase 2 report. A brief summary is repeated here for 

continuity, and to serve as an introduction to the technology for anyone unfamiliar with 

the technology. 

FSO dates to pre-history. Extensive FSO networks were established in the 19th Century 

throughout France and North Africa, based on semaphore systems. Later, during the 

latter part of the 19th century, FSO telephone communication was developed. 

The modern FSO age commenced with the invention of the laser slightly more than 45 

years ago. Generation of wavelength stable coherent light at selected wavelengths 

6
ECT – Phase 4 

 

provided the ability to select specific fixed wavelengths to achieve FSO systems that 

enable lessening atmospheric attenuation, provide operation through rain, and achieve 

eye-safety. 

Fundamentally, modern FSO systems typically employ NRZ (non-Return to Zero) 

modulation of laser light. Digital data is encoded as either a high intensity beam or as a 

low intensity beam, separated by the extinction ratio present in the ON to OFF states 

engendered by the modulating device. 

Within the receiver, a photodetector provides the optical to electrical (OE) conversion. 

Depending on the range over which communication is desired, both Positive-IntrinsicNegative (PIN) diodes and APDs (Avalanche Photodetector Diodes) are used. PIN 

diodes provide less sensitivity, but require only minimal voltage bias to make them 

operational. APDs provide the maximum performance in sensitivity, but require voltages 

often exceeding 100 Volts dc to achieve this high sensitivity. This, in turn, increases the 

need for properly coating circuit cards for FSO apparatus intended for use outdoors, to 

avoid issues with condensing moisture causing short-circuits. 

At the output of the photodetector is a Trans-Impedance Amplifier (TIA). Its purpose is 

to provide the necessary gain by which to generate a voltage from the current produced 

by the photodetector diode when exposed to light. Beyond this lie the framing and other 

packetizing electronics, needed to provide the proper data interfaces for the subsequent 

parts of the communication system. For fiber optic extensions, it is necessary to have 

clock and data recovery circuitry, by which clocks are derived from incident light pulses 

coming into the FSO system via fiber optic cable, to provide proper timing interfaces. 

For the fSONA system tested on this project, a Smartbits OC-12 fiber optic interface 

operating at 622 Mb/s served as the physical data interface in and out of the two OTUs. 

Advantest and Anritsu pattern generators and error detectors were also used at times for 

performing these same duties during SLF testing. 

2.3 TEST DESCRIPTION 

Phase 4 testing with FSO units included two FSO systems, tested at four locations over 

various distances. Most of the FY05 testing was performed with the fSONA 622-M 

system. A short test was also run using the AirFiber units procured during Phase 2. Test 

locations included the following: 

• SpaceHab optical laboratory 

• EDL building rear parking lot 

• Schwartz Road 

• Shuttle Landing Facility (SLF) 

7
ECT – Phase 4 

 

2.4 TEST OBJECTIVES 

The FSO test objectives were as follows: 

• Evaluate COTS FSO equipment for possible future use at KSC 

• Identify any fundamental shortcomings that must be filled in commercial FSO 

communication technologies prior to integrating these technologies into future 

range architectures 

• Compare a fixed alignment, multiple beam, wide beam system against the 

previously-tested auto-tracking, single beam, narrow beam FSO system 

• Investigate scintillation and other atmospheric limitations on FSO, and assess 

aperture averaging mitigation on Bit Error Rate (BER) 

2.5 TEST LOCATIONS & SETUPS 

Test setups varied by location and equipment. A pair of antenna trailers were modified 

during earlier phases of ECT to enable quick mounting of either the fSONA or AirFiber 

FSO systems. These trailers were used for all outside testing and enabled quick 

positioning of the FSO systems. A pair of portable stands were used for indoor testing of 

the fSONA units. 

For outdoor testing, the basic test setup was to position the two trailers at a fixed 

distance, align the Optical Transfer Units (OTU), establish a data link, test the quality of 

the link and then conduct any scintillation and aperture averaging mitigation 

measurements. 

Initial alignment of the fSONA system was accomplished using a 12X power LeupoldTM 

rifle scope. This gross alignment was usually adequate to establish an initial, but not 

optimally aligned link. The link was then electronically fine-tuned using the factory 

provided software on a laptop computer. This software provides an output display of the 

receiver’s incoming energy in microwatts. Mechanical adjustment was accomplished 

using jacking screws on both azimuth and elevation lever arms. Once the alignment was 

completed, the azimuth and elevation axes were locked and not changed further during 

testing. 

The AirFiber units were aligned using their internal cameras and their self alignment 

feature. The OTU were aligned by mechanically positioning each OTU with its target 

OTU in the camera’s field of view. The internal crosshairs were driven to center on the 

peer OTU and then the system’s auto-alignment feature was activated. The AirFiber 

system then automatically located, centered, and maintained both OTUs for an optimum 

link. 

A SmartBits Bit Error Rate test device was used to test and verify the initial quality of the 

fSONA link. Early during testing, it was discovered that establishing a link based only 

the receive power and the fSONA status indicator was not adequate to ensure a solid link. 

8
ECT – Phase 4 

 

Instead, we found it necessary for the SmartBits to measure throughput and packet loss 

for various packet sizes to ensure a solid link. This setup is shown in Figure 2-1. The 

SmartBits sent a variable length data stream to the input of OTU #1. OTU #1 transmitted 

the data packets to OTU #2 using the FSO laser. OTU #2 received the FSO data packets, 

and converted these to a multi-mode fiber-optic output. This output was looped back to 

the input of OTU #2 through a short fiber optic cable jumper. The data packets were then 

converted back to another FSO signal and sent back along the same propagation path 

from OTU #2 to OTU #1. The fiber output from OTU #1 was directed back to the 

SmartBits where a comparison was made between the transmitted and received packets to 

determine any throughput errors or packet losses. 

After the initial link was established and verified with the SmartBits, additional 

equipment was used to measure the Bit Error Rate (BER) with more flexibility in the 

choice of specific maximal length test sequences than possible with the SmartBits, 

setting (i.e., PRBS 23), typically, although setting 

2 1 N −

N = 23 N = 21 and lower was also 

used on occasion for trouble-shooting test configurations. A typical test setup is shown 

in Figure 2-2. Specifically, an Advantest D3186 Pattern Generator was used to input a 

test pattern (usually PRBS 23) to OTU #2. This data pattern was sent via FSO to OTU 

#1 using only one of the four laser transmitters (Tx). The fiber output from OTU #1 was 

then routed to an Agilent 83440C Receiver that converted it to an electrical signal. The 

electrical signal was then sent to a Mindspeed M21012 Clock & Data Recovery (CDR) 

unit. The data and clock outputs from the CDR went to an Advantest D3286 Error 

Detector where the BER measurements were made. For some tests, an Anritsu MP1763C 

Pattern Generator and an Anritsu MP1764A Error Detector were substituted for the 

Advantest equipment. Measured BERs would vary by test as the receive area of fSONA 

#1 was reduced using aperture masks and scintillation varied due to diurnal variation of 

solar heating of the SLF. Masks and test equipment are discussed in more detain in a 

later section. For Scintillation testing, the setup also included a Scintec BLS900 

Scintillometer and Cambell Scientific Weather Station. 

ASRC Aerospace personnel ran the fSONA and SmartBits equipment, and performed 

alignment of the FSO links. FSI personnel provided and ran the pattern generators, error 

detectors, weather station and scintillometer. 

The choice of test location was selected based on the purpose of the test and the distance 

to be investigated. The SpaceHab Optical Lab was used for very short distance 

laboratory testing. The EDL parking lot was used to verify test setups prior to deploying 

into the field for longer distances. Schwartz Road was used for distances up to 2.5 miles 

when scintillation effects were not being investigated. The SLF was utilized for its 

controlled environment while doing 1 km testing of scintillation effects. A summary of 

test locations and distances is included in Table 2-2. Testing was not performed in any 

specific order. Details about each test location are included in the following sections. 

The FSO units, test equipment and software are described in later sections. 

9
ECT – Phase 4 

 

OTU #1 OTU #2 

 

 Fiber 

 Loop-back 

 SmartBits 

 Laptop Laptop 

Figure 2-1 Typical Link-Verification Setup Using SmartBits 

 

 Scintillometer 

 

 1 Tx 

 Tx @ 1 O’clock 

 

 

 1.0” to 8.0” Aperture 

 

 Wx 

 

CDR 

fSONA 

 Rx #1 

Pat 

Gen 

fSONA 

#2 

Err Det 

 Laptop Laptop 

Figure 2-2 Typical BER Test Setup 

10
ECT – Phase 4 

 

Table 2-2 FSO Test Locations 

Location One Way Distance Loop Back 

SpaceHab Optics Lab 10 ft N 

EDL East Parking Lot 175 ft Y 

Schwartz Road 1.0 to 2.5 miles Y 

SLF 1000 km Y/N 

2.5.1 SpaceHab Optical Laboratory

SpaceHab is a payload processing facility owned by AstroTech and located just outside 

the Cape Canaveral Air Force Station south gate. Office space and facilities are also 

leased to others in the space industry. The Florida Space Institute (FSI), a part of the 

University of Central Florida (UCF), maintains an optical laboratory at this facility. 

The fSONA units were removed from their trailers and taken to the FSI Optical 

Laboratory at SpaceHab for precise testing and characterization. The fSONA units were 

mounted on their short support stands that were fabricated during Phase 3. These stands 

were placed on a 10-foot optical table inside the environmentally controlled optical lab. 

During the subsequent tests, only a single transmitter on OTU #1 was used as the signal 

source. Due to the close proximity of the OTUs, calibrated attenuators were mounted to 

the exterior of the 1 O’clock transmitter. The other three transmitters were turned OFF. 

Figure 2-3 shows the test setup within the lab. Figures 2-4 and 2-5 provide additional 

views of the laboratory testing and some of the test equipment. Newport and Ophir 

power-meters were used during the tests. One series of tests measured receive power at 

OTU #2. Another series measured the laser beam power and signal at a position between 

OTU #1 and OTU #2. FSI research associates from Harris Corporation performed these 

measurements. 

11
ECT – Phase 4 

 

Figure 2-3 SpaceHab Optical Lab Setup 

Figure 2-4 fSONA Units Being Tested In The SpaceHab Optical Lab 

12
ECT – Phase 4 

 

Figure 2-5 Beam Measurements Between OTU #1 & OTU #2 

13
ECT – Phase 4 

 

2.5.2 EDL East Parking Lot

The EDL East parking lot is a convenient location for conducting initial shake-down, 

procedural, and other preliminary tests where long distances are not required (Figure 2-

6). Trailers are usually positioned about 175 feet apart. Figure 2-7 shows fSONA #1 

mounted on Trailer #1 located on the North end of the parking lot (left). Figure 2-8 

shows Trailer #2 & fSONA #2 on the South end of the parking lot (right). Portable 

generators are used for power during these tests. The tests were usually set up per Figure 

2-1. 

Figure 2-6 EDL Parking Lot 

Figure 2-9 shows both the AirFiber and fSONA units mounted on Trailer #1. The 

AirFiber units were tested to verify they were operational and to compare and contrast 

their auto-alignment process with the fSONA’s manual alignment process. The AirFiber 

and fSONA OTUs could not be simultaneously used on the trailers because the signal to 

fSONA #1 on Trailer #1 would be blocked by AirFiber #1. 

14
ECT – Phase 4 

 

Figure 2-7 OTU-1 in EDL Parking Lot 

Figure 2-8 OTU-2 At South End of EDL Parking Lot 

15
ECT – Phase 4 

 

Figure 2-9 AirFiber #1 On Trailer #1 in EDL Parking Lot 

2.5.3 Schwartz Road Test Setup

Schwartz Road is a remote East-West road at KSC that runs relatively straight for 2.7 

miles. During Phase 3, extensive long-distance testing of the fSONA units was 

performed on Schwartz Road. Some additional testing was also performed at this 

location during Phase 4. This testing was primarily run to verify the baseline values of 

the fSONA units prior to SLF testing. Trailer #2 with fSONA #2 was placed in the 90-

degree bend on the West end of Schwartz Road (Figure 2-10). Trailer #1 was positioned 

off to the side of the road at various distances (Figure 2-11). Initial testing was 

performed at 1.0 mile. This was followed with practice tests at 1.0 km. The baseline test 

configuration was again per Figure 2-1 with the SmartBits and Laptop positioned on 

trailer #1 and a fiber loop-back installed at OTU #2. Power was provided by a portable 

generator. BER tests were per Figure 2-2 without the weather and scintillation 

equipment. All equipment was run off a single portable ac generator at each end. 

16
ECT – Phase 4 

 

Figure 2-10 OTU #2 Parked In The Bend On The West End of Schwartz Rd. 

 

Figure 2-11 OTU #1 Positioned @ 1 Km On Schwartz Rd. 

17
ECT – Phase 4 

 

2.5.4 Shuttle Landing Facility

All scintillation testing was performed under the controlled environment of the Shuttle 

Landing Facility (SLF). Its controlled shape, orientation, and uniformity make it an 

ideal laser test range. Figure 2-12 is an aerial view from the North end of the SLF. The 

VAB is visible near the top left. General specifications for the SLF are as follows: 

• 15,000 feet active runway 

• 300 feet wide 

• Precisely grooved and milled surface 

• Orientation: 150 / 330 Degrees 

The SLF is an active airport when the Space Shuttle is not landing (Figure 2-13). This 

limits the days and hours of testing. Special rules and safety training are also required. 

The testing setup at the SLF followed the same configuration at the other sites. The 

trailers with the fSONA units onboard were positioned 1000 meters apart on or near the 

centerline of the SLF. Unit #1 was always on the South side (Figures 2-14 & 2-15) and 

Unit #2 on the North side. Unit #1 was always located at the 3000-foot mark referenced 

from the South runway edge (concrete portion) of the SLF. The 3000-foot location was 

selected since the first 3000 feet have had the rain grooves removed. The fSONA units 

were usually placed on the centerline of the SLF except for some later tests that included 

a pair of FSI equipment trailers. For these latter tests, the FSI trailers were placed on the 

centerline and the fSONA units were moved 20 feet east of the centerline (Figure 2-16). 

Figure 2-12 SLF Viewed From North 

18
ECT – Phase 4 

 

Figure 2-13 Typical Aircraft Traffic at SLF 

Figure 2-14 fSONA #2 on SLF Centerline 

19
ECT – Phase 4 

 

Figure 2-15 fSONA #1 With SmartBits, Laptop & Open Control Panel 

Figure 2-16 SLF South Setup With fSONA #1, FSI Trailer, and Scintillometer 

20
ECT – Phase 4 

 

Once the trailers were in place, the units were aligned both mechanically and 

electronically. The mechanical alignment was accomplished via a 12X riflescope using 

jacking screws on both azimuth and elevation axes. Electronic alignment employed 

using the same jacking screws to obtain a peak receive power using the factory software. 

During latter tests, alignment was based on peak receiver voltage at the output ports 

inside the control panel (Figure 2-15). The voltage was read using a digital multi-meter. 

This method tended to provide a quicker readout with less noise. The verification setup 

was as previously shown in Figure 2-1. Tests using the SmartBits, seen under the laptop 

in Figure 2-15, confirmed a good link was established. Throughput values of 100% and 

packet losses of 0% were usually achieved for all packet sizes. 

Alignments were performed early in the day prior to the presence of the worst of the 

day’s scintillation using a loop-back link from the far-end to the near-end, traversing the 

1 km span twice. Once aligned, one-way scintillation tests were then conducted through 

local solar noon, collecting measured data of BER versus receive aperture diameters. 

BER testing was then performed in conjunction with the University of Central Florida 

and the Florida Space Institute per Figure 2-2. The BER measurement equipment was 

inside the FSI trailer shown to the left in Figure 2-16 or inside the van shown in Figure 2-

17. The scintillometer receiver is visible under the left edge of the awning in Figure 2-

16. 

21
ECT – Phase 4 

 

Figure 2-17 South SLF Setup With Van and Trailer 

2.6 TEST EQUIPMENT AND SOFTWARE 

Key FSO test hardware included the following: 

• SONAbeam 622-M - Optical Transceiver Unit (OTU) 

• AirFiber 5800 OC-12 - Optical Transceiver Unit (OTU) 

• SmartBits – Data packet source for measuring Throughput and Packet Loss 

• Advantest D3186 – 10 Gbps Pattern Generator 

• Advantest D3286 – 10 Gbps error Detector 

• Anritsu M1763C – 10 Gbps Pattern Generator 

• Anritsu M1764A – 10 Gbps Error Detector 

• Agilent 83440C 20 GHz Receiver 

• Mindspeed M21012 - Clock and Data Recovery 

• Campbell - Scientific Weather Station 

• Scintec BLS900 - Scintillometer (Transmitter & Receiver) 

In addition to the above hardware, software packages were instrumental in testing and 

data acquisition. These software packages included: 

• SONAbeam’s STCv3 - Terminal Control Software 

• AirFiber’s CamLAP – Link Acquisition Program 

• SmartBits’s SmartApplications – Packet Testing Program 

• LabView BER calculations & Data Acquisition 

• Scintec operations software 

• Campbell Scientific Wx Station operations software 

2.6.1 SONAbeam 622-M

The SONAbeam 622-M OTU, shown in Figure 2-18, was the primary component under 

test. Specifications for the units are summarized in Table 2-3. A pair of 622-M were 

purchased around 3/1/04 under the ECT task order (#00087), Phase 3. 

The SONAbean 622-M is a fixed alignment, multi-beam design. Initial alignment is 

normally achieved using an eye-safe unfiltered 12x power rifle scope at longer distances, 

and a lower-power eye-safe filtered 9x rifle scope at shorter distances. Fine alignment is 

achieved using the fSONA software or a voltmeter. 

22
ECT – Phase 4 

 

Figure 2-18 Front of SONAbeam 622-M OTU 

The units came with a factory-supplied junction box. The inside of the box is shown in 

Figure 2-19. Payload fiber, management Ethernet, and power connections are made 

within this box. The two orange fibers to the right are the multi-mode fibers connecting 

the SmartBits to the OTU. Also visible on the lower fiber is the 10 dB attenuator inserted 

in the output line to enable the OTU and SmartBits to communicate. Figure 2-20 shows 

the junction box mounted on the support pole just below the OTU. The smaller utility 

box in this figure is the in-house fabricated power supply housing. It contains the 110 

vac to -48 vdc power supply. 

Table 2-3 SONAbeam 622-M Specifications 

23
ECT – Phase 4 

 

Manufacturer fSONA Communication Corp 

140-11120 Horseshoe Way 

Richmond, B.C. Canada 

Model SONAbeam 622-M 

Cost $40,522.69/pair w/training 

Purchase Date 3/15/04 

Data rate OC-12 (622 Mbps) 

Range Max mi / m 3.4 / 5500 

Transmitters No. 4 

Tx Type Directly modulated laser diode (OOK) 

Tx Wavelength nm 1550 

Tx Power mW 560 (4 x 140) 

Tx Beam Divergence (nominal) mRad 2 

Receiver Type APD 

Receiver Dia in/cm 8 / 20 

Auto-track No 

Interfaces Types Fiber Single mode or Multi-mode 

Interface Connector Data SC 

Management RJ-45 or DB9 

Voltage -48 vdc 

BER 10-12

Environment Max Operating Temp 140 F 

 Max Operating wind 100 mph 

Laser Safety Class 1M (eye safe) 

Assigned IP Address #1 128.217.108.178 

 #2 128.217.108.179 

Assigned Subset Mask #1 & #2 255.255.255.0 

Assigned Gateway #1 & #2 128.217.108.10 

Serial Numbers #1 1130050858 

 #2 1130030756 

. 

24
ECT – Phase 4 

 

Figure 2-19 SONAbeam Junction Box Open 

Figure 2-20 Pole Mount with OTU, Connection Box & Power Supply Box 

25
ECT – Phase 4 

 

Bit errors were forced by choking down the receiver area of fSONA #1 using aperture 

masks that blocked a large portion of the 8-inch receiver aperture. Both fixed and 

variable area masks were used. Figure 2-21 shows a mask with a variable area aperture 

and two fixed apertures. The fixed apertures are taped over to make the variable units the 

only active area. A mask adapter was machined and attached to the receiver shroud on 

fSONA #1. This adapter allowed for the quick installation and positioning of the masks. 

Positioning was achieved by rotating the mask opening until the “sweet spot” was 

obtained. Aperture openings were machined off center since the internal geometry of the 

fSONA receivers blocks the center 1-inch diameter. In addition, the 12 and 6 o’clock 

positions are blocked by internal support struts. Multiple openings were machined in 

various masks, but only one opening was used at a time. The others were covered with 

tape. Tests were conducted with Aperture diameters of 8.0, 3.0, 2.0, 1.25 and 1.0 inch. 

Figure 2-22 is a close-up of the variable size aperture. 

Figure 2-21 Aperture Adapter and Mask 

26
ECT – Phase 4 

 

Figure 2-22 Aperture Adapter and Mask 

27
ECT – Phase 4 

 

2.6.2 AirFiber 5800

The AirFiber FSO system uses single beam AirFiber 5800 OTUs, each with auto-track 

capability. The OTU is shown in Figure 2-23 with its fiberglass shroud removed. The 

auto-track feature and the built-in cameras enable both OTUs to quickly self-align 

themselves to provide an optimum link. The AirFiber system includes communication 

and feedback between the two OTU peers. During operation, the auto-track feature 

maintains optimum performance even with slight wind loads or building movements due 

to uneven diurnal or seasonal heating. The trailer-mounted AirFiber OTUs were tested 

only in the EDL parking lot at a distance of about 175 feet. The tests confirmed the 

AirFiber units were fully operational after two years of storage. Specifications for these 

units are presented in Table 2-4. 

Figure 2-23 AirFiber 5800 With Fiberglass Shroud Removed 

28
ECT – Phase 4 

 

Table 2-4 AirFiber 5800 Specifications 

Manufacturer AirFiber 

San Diego, CA (Out of Business 2/26/03) 

Model 5800-0623-MM 

Cost $23,724 /pair w/training 

Purchase Date 12/12/02 

Data rate OC-12 (622 Mbps) 

Range Max mi / m TBD 

Transmitters No. 1 

Tx Type TBD 

Tx Wavelength nm 785 

Tx Power mW 18 

Tx Beam Divergence (nominal) mRad 0.5 

Receiver Type APD 

Receiver Dia in/cm 3 / 7.5 

Auto-track Yes 

Interfaces Types Fiber Single mode or Multi-mode 

Interface Connector Data SC 

Management RJ-45 or RS-232 

Voltage -48 vdc 

BER 10-12

Environment Max Operating Temp 170 F 

 Max Operating wind 120 mph 

Laser Safety Class 1M (eye safe) 

Assigned IP Address #1 128.217.108.176 

 #2 128.217.108.177 

Assigned Subset Mask #1 & #2 255.255.255.0 

Assigned Gateway #1 & #2 128.217.108.10 

Serial Numbers #1 00025000001017 

 #2 00025000001035

29
ECT – Phase 4 

 

2.6.3 SmartBits

An existing SmartBits, shown under the laptop in Figure 2-15, was used to verify the link 

quality for the fSONA units. The SmartBits created varying size data packets that were 

sent through the FSO communication link at OC-12 data rates. The SmartBits compared 

the data sent with the data received and produced a report on Throughput and Packet 

Loss. 

The SmartBits was populated with a pair of ATM OC-12 driver cards in slot positions 17 

and 19. For these tests, Card 19 was usually the transmitter and Card 17 was the 

receiver. A jumper fiber was also connected from the Card 19 Rx to the Card 17 Tx to 

complete the circuits. Figure 2-24 shows an earlier field test setup on Schwartz Rd. 

. 

Figure 2-24 Field Testing with the SmartBits & a Laptop 

2.6.4 Pattern Generators

Two different but interchangeable pattern generators were used during Scintillation 

testing. The primary unit was an Advantest D3186 10 Gbps pattern generator. The 

Anritsu MP1763C was also used for some tests. This equipment was provided and 

operated by FSI personnel. 

30
ECT – Phase 4 

 

2.6.5 Error Detectors

Two different but interchangeable error detectors were used during Scintillation testing. 

The primary unit was an Advantest D3286 10 Gbps error detector. The Anritsu 

MP1764A 10 Gbps unit was also used for some tests. This equipment was provided and 

operated by FSI personnel and located within the FSI trailer or van. 

2.6.6 Receiver

An Agilent 83440C 20 GHz receiver was used downstream of fSONA #1 to convert the 

optical output for the fSONA to an electrical signal. This was necessary because both 

brands of error detectors required electrical inputs as opposed to fiber inputs. This 

equipment was provided and operated by FSI personnel and located within the FSI trailer 

or van. 

2.6.7 Clock and Data Recovery (CDR)

A Mindspeed M21012 CDR was used to separate the clock and data signals and prepare 

them for error detector measurements. This equipment was provided and operated by 

FSI personnel and located within the FSI trailer or van. 

2.6.8 Weather Station

Local weather data was measured using a Campbell Scientific weather station shown on 

the left in Figure 2-25. The weather station had its own control and data logging 

software that ran on a laptop. The station was later mounted on its own trailer. This 

equipment was provided and operated by FSI personnel. 

2.6.9 Scintillation

A Scintec BLS900 scintillometer was used during SLF testing. The receive unit is shown 

in Figure 2-25 on the right of the weather station. The transmit section is shown in 

Figure 2-26. The two components were positioned 1 km apart, the same as the FSO 

units. This equipment was provided and operated by FSI personnel. 

31
ECT – Phase 4 

 

Figure 2-25 Wx Station and Scintillometer Rx on SLF 

Figure 2-26 Transmit Portion of Scintec Scintillometer 

32
ECT – Phase 4 

 

2.6.10 SONAbeam Terminal Controller Software

The main Operating System for the fSONA 622-M is the Terminal Controller Software. 

An upgraded version was loaded prior to the Phase 4 tests. The software description 

provided in the Phase 3 report still applies. 

2.6.11 SmartApplications

SmartApplications is the operating system software for the SmartBits. This software was 

described in the ECT Phase 3 report. 

2.7 TEST RESULTS 

FSO testing consisted of measurements at four test locations with two types of tests at 

each location. The four locations and the general test objectives at each are summarized 

in the following table. 

Table 2-5 Summary of Test Locations & Objectives 

Location Test Objectives 

SpaceHab Laboratory measurements of fSONA output power 

and receiver configuration 

EDL East Parking Lot AirFiber OTU checkout, fSONA OTU checkout & 

procedure testing 

Schwartz Road Baseline testing and SLF dry run testing 

SLF Scintillation effect testing at 1 km 

FSO testing was conducted from November 2004 through August 2005. Initial testing 

was delayed by recovery efforts from Hurricanes Charley and Frances. During the test 

period, the fSONA 622-M units worked without any noticeable problems. The most 

difficult part of operating the OTUs was establishing the initial FSO link alignment and 

link performance. The AirFiber 5800 OTUs were found to be fully operational. 

2.7.1 Prior Art and Historical Rationale for Testing Methodology

33
ECT – Phase 4 

 

Recent research on the effects of optical scintillation on the probability of error, or bit 

error-rate (BER), involved the extension of the Rytov approximation into the strong 

fluctuation regime5 and the use of a (spatially) partially-coherent source.6 These 

advances in the theory enable addressing optical scintillation degradation concerns for 

evaluating a wide range of future lasercom needs, including Earth-to-Mars, Earth-toorbit, and Earth-to-Moon FSO links. 

For addressing the theoretical limits that exist for another set of future FSO needs, such 

as for achieving higher efficiency lasercom systems for terrestrial point-to-point links, 

enabling communication through rocket exhausts with FSO systems, developing lowered 

probability of intercept covert communication systems, and enhancing military laser 

target designator weapons systems, more complex theories of optical scintillation, for 

predicting both amplitude and phase variations, are needed. After all, as documented in 

prior NASA research at JPL, space-to-ground links for satellite lasercom applications 

involve beam propagation through less air mass than horizontal terrestrial path links 

exceeding 10 km in length.7 The terrestrial point-to-point FSO links operating over 

longer distances are more difficult links to close than the more esoteric longer range and 

more glamorous Earth-to-Mars, orbit, and Moon links. 

Classical approaches to studying optical wave propagation are based primarily on 

studying simplified uniform plane wave and spherical wave models. Plane wave models, 

for example, are often used in describing the properties of starlight or laser beams 

passing through the Earth’s atmosphere from space. Zernike’s phase contrast method of 

observation involves assuming the existence of a phase object which alters the phase but 

not the amplitude of an incident plane wave.8 Unfortunately, such simplified approaches 

do not account for the various effects that are caused by the finite size of a beam wave 

and its diverging and focusing capabilities. 

The traditional method to address and overcome the limitations of simplified modeling 

approaches is to develop theory for a basic wave model based on the lowest order 

Gaussian-beam wave, which is characteristic of a single transverse electromagnetic wave 

(TEM00). This approach has the advantage of developing optical scintillation theory that 

provides, as limiting cases, the same results as have been previously shown by the earlier 

classical approaches. It also permits enhancing one’s ability to address many of the firstlevel concerns that result from assuming a random media such as the atmosphere, for 

which small index-of-refraction fluctuations induced by random temperature variations 

are the primary concern.9

 

5

 L. C. Andrews, R. L. Phillips, and C. Y. Hopen, Laser Beam Scintillation with Applications (SPIE Press, 

Bellingham, WA (2001). 

6

 O. Korotkova, L Andrews, R. Phillips, “Model for a partially coherent Gaussian beam in atmospheric 

turbulence with application in Lasercom,” Opt. Eng. 43(2) 330-341 (Feb. 2004). 

7

 A. Biswas, M. Wright, B. Sanii, N. Page, “45 Km horizontal path optical link demonstrations,” Proc. 

SPIE 4272, 60-71 (2001). 

8

 M. Born, E. Wolf, Principles of Optics, Pergamon Press, New York, NY (1975), Fifth Edition, pp. 424-

428. 

9

 L. C. Andrews, R. L. Phillips, Laser Beam Propagation through Random Media, SPIE Press, 

Bellingham, WA (2001). 

34
ECT – Phase 4 

 

Optical scintillation theory developed in this way is entirely consistent with Born and 

Rytov weak fluctuation theories, and permits developing spectral representations for the 

first-order and second-order complex phase perturbations that are consistent with the 

Rytov approximation.10 Building off an extended version of the Rytov approximation is 

a method that characterizes optical scintillation into the focusing and saturation regimes. 

This extension of the conventional Rytov theory is based on the notion that only scale 

sizes smaller than the spatial coherence radius or larger than the scattering disk contribute 

to optical scintillation under moderate-to-strong irradiance fluctuations. The theory has 

also been extended to account for large receiver apertures that lead to a reduction in 

scintillation known as the averaging effect. 

For the measurements made at the SLF to validate these previously unvalidated theories, 

two commercially-available instruments built by fSONA were used for the optical 

transmitter and receiver to perform the experiments. The purpose of the experiment was 

to measure the effect of aperture averaging on the BER and additionally to compare these 

measurements with the published theory. Thus, various aperture sizes were used at the 

receiver end of the propagation path to study the decrease (improvement) in BER as the 

size of the receiver aperture was increased. Because the theory of optical scintillation in 

moderate-to-strong fluctuation regimes is relatively new, it has not been satisfactorily 

validated through the collection of experimental data. Consequently, the taking of 

experimental data is key to determining the limitations of this optical scintillation theory, 

and to validate its use in future a priori communication link planning activities in and 

around Kennedy Space Center. 

2.7.2 Testing Methodology

The basic characteristics of the commercial instruments used during the experiments 

were described in Table 2-3. The nominal free-space diameter of the spot size in the 

receive plane of the lasercom beam from the laser beam divergence was 2 meters, typical 

for a 1 km spacing between transmitter and receiver. Even under fairly strong turbulence 

conditions (i.e., ), the beam diameter was only a few centimeters larger 

than 2 meters. Artificially reducing the receiver aperture from the 20-cm (8-in nominal) 

effective clear aperture, by controlling aperture mask diameters at the receiver, allowed 

simultaneously reducing receiver power levels while affecting signal to noise ratios 

within the data rate bandwidth. This permitted studying the effects of aperture averaging 

of scintillation effects for larger aperture masks on BER, at power levels for which 

moderate numbers of errors would occur during a reasonable time. 

2 13 Cn ~ 5 10 m − × -2/3

 

In addition to the normal factory-standard hardware of the fSONA SONAbeam 622-M, 

we sometimes added external neutral-density filters to the transmitting lasers. These 

transmitting laser add-ons enabled us to achieve more precisely calibrated control of the 

10 L. C. Andrews, R. L. Phillips, Laser Beam Propagation through Random Media, SPIE Press, 

Bellingham, WA (2001), Chapter 5. 

35
ECT – Phase 4 

 

transmitting laser power, as needed to achieve the desired signal-to-noise ratios in the 

optical receiver as required to study bit error rates. Although reducing the aperture 

reduces the signal power and external noise power equally, which clearly has no impact 

on the signal-to-noise ratio, the internal noise power is not reduced by reducing the 

aperture mask diameter. Hence, reducing the aperture diameter can be used to vary the 

signal-to-noise ratio due to the presence of internal noise. 

2.7.3 Instrument Operation

Atmospheric conditions were continuously monitored during the experiments. Average 

values of refractive-index structure parameter, Cn

2

, were provided by a Scintec BLS900 

scintillometer over the time period of data collection. In particular, measured values of 

Cn

2

 that were averaged over one minute periods are shown in Figure 2-27. Typical 

values were in the range of 10-14 to more than 10-13 m-2/3. This same scintillometer 

instrument also provided the average cross wind speed during the time period of each 

experiment. Other environmental data instrumentation included a weather station that 

gave wind speed and direction, temperature, humidity, visibility, cloud ceiling, solar 

irradiance, atmospheric pressure, and runway surface temperature. 

11 12 13 14 15 16

Time of Day

3

4

5

6

7

8

9

Inner Scale (mm)

June 3, 2005

1-minute averages

Figure 2-27 Measured Average Cn

2

 Values

The outer scale of turbulence L0 was estimated to be 1 m, equal roughly to half the height 

of the optical wave path above ground. Values of the inner scale of turbulence l0 were 

inferred from the surface roughness of the Shuttle Runway and average wind speed, i.e. 

36
ECT – Phase 4 

 

3/4 l const V 0 ~ ./ , where V denotes the average wind speed. One minute average values of 

the wind speed produced the inner scale values shown in Figure 2-28. Typical values of 

the inner scale calculated by this method were between 3 and 7 mm. 

11 12 13 14 15 16

Time of Day

3

4

5

6

7

8

9

Inner Scale (mm)

June 3, 2005

1-minute averages

Figure 2-28 Values of Inner Scale from 1-min. Avg. Wind Speed

In addition to environmental data instrumentation, bit error rate data collecting 

instrumentation was also used during the experiments. An OC-12 SONET rate signal at 

622.08Mbps was generated using an Advantest D3186 Pattern Generator (PG). The PG 

was configured to generate an NRZ-coded pseudo-random bit sequence (PRBS) 2^23-1 

pattern data stream with a 1⁄2 mark ratio. There was no framing present on this signal. 

This PRBS signal drove a custom electro-absorption modulated laser (EML). This 

modulated laser signal was then attenuated to a level that matched the acceptable 

operating input optical levels of the fSONA optical transceiver. Within the fSONA 

transceiver, this optical signal was regenerated and then used to drive any or all of the 

four fSONA internal 1550nm Fabry-Perot laser transmitters. Throughout the majority of 

our experiments, only one of the fSONA transmitters was configured to be active at any 

one time. Prior to running SLF range experiments, this particular transmitter was first 

thoroughly characterized in a controlled optical lab bench environment using various 

calibrated instruments. We experimentally measured laser transmitter properties 

including linewidth, output power level settings, beam diameter, stability, extinction 

ratio, and eye diagrams, all of which combined to help us better understand the 

limitations of the hardware and to determine which optical transmitter power levels 

would be best suited for use during experiments. 

37
ECT – Phase 4 

 

The transmitted signal from the fSONA transmitter terminal was sent through free space 

(1 km) and entered the fSONA receiver terminal. The receiver terminal focused the 

collected 1550nm light onto an Avalanche Photo Diode (APD). This received optical 

signal was then regenerated inside the fSONA terminal using a trans-impedance amplifier 

(TIA), pre-amplifier, bandpass filter, post-amplifier, and limiter. The recovered data 

stream was then used to drive another internal laser to transport the received data out of 

the fSONA receiver terminal. Once the signal was removed from the fSONA receiver 

terminal, we needed to sample it again to recover the original transmitted pattern from 

our PG on the transmitter side. This was done using a high-sensitivity, multi-mode, 

2.5Gbps multi-rate receiver module. This module drove a clock and data recovery (CDR) 

circuit which then fed the recovered data and clock to the Anritsu D3286 Error Detector. 

Automated instrument drivers controlled and synchronized data collection among the 

scintillometer, weather station and the fSONA’s received optical power meter during the 

entire time that data was collected. 

2.7.4 Theoretical Equations

The modulation format of the SONAbeam 622-M FSO equipment used in this study is 

considered to be bounded by the theoretical performance of OOK (ON-OFF Keying), 

despite being NRZ-coded (non-return-to-zero coded). This modulation type is chosen 

because the receiver does not take advantage of coherent methods of detecting 

transmitted NRZ coded signals, but instead uses only non-coherent OOK detection 

techniques. The significance of this is that the theoretical performance of the FSO 

equipment used is 3 dB worse than if coherent NRZ decoding were used. 

Probability of error, which determines the theoretical Bit Error Rate (BER) curve 

performance, is given for NRZ-coded electrical data by11

( 1

2 Pr( ) erfc E = ⋅ z )

 

 (1) 

where erfc(x) denotes the complementary error function and z is the data signal to noise 

power ratio. This same probability of error equation applies equally for any antipodalencoded modulation (e.g., NRZ, BPSK, PRK, etc.) in which the cross-correlation, , 

equals -1 between the two signaling states.

12 R

12 It does not, however, express the predicted 

probability of error for OOK (ON-OFF Keying.) For OOK (which is orthogonal-encoded 

modulation), the cross-correlation between the two signaling states equals zero, and this 

shifts the theoretically-predicted BER curve 3-dB worse than antipodal signaling for the 

11 R. Ziemer, W. Tranter, Principles of Communications, Systems, Modulation, and Noise, Houghton 

Mifflin Co., Boston, 1976, pp. 315-316. 

12 R. Ziemer, W. Tranter, Principles of Communications, Systems, Modulation, and Noise, Houghton 

Mifflin Co., Boston, 1976, pp. 319-320. 

38
ECT – Phase 4 

 

required signal-to-noise ratio that is necessary for achieving any particular desired BER 

performance.13

OOK is also sometimes called Intensity Modulated Direct Detection (IM/DD). In 

practice, true OOK is difficult to achieve for FSO systems, which are limited by the 

extinction ratios existing between the two states. OFF is never truly OFF. For the 

equipment used in this experiment, an extinction ratio of approximately 10 dB is all that 

is achieved for the ‘OOK modulation’ encoded states by the hardware. Despite being 

‘OOK-decoded’, the effective modulation encoding is therefore actually NRZ-encoded 

for the hardware used in this experiment. The theoretical BER limits pertaining to NRZ 

rather than to OOK are most applicable for predicting absolute theoretical BER 

performance curve limits. However, due to non-coherent receiver operation, the 

theoretical BER limits for OOK (IM/DD) remain more representative for predicting the 

measured performance of the hardware under investigation. Hence, a choice of 

comparing against the theoretical BER curve pertaining to OOK (IM/DD) is taken as the 

appropriate theoretical limit for the present investigation, despite giving up 3-dB from the 

actual theoretical limit that also exists. 

OOK additionally provides by far the better BER analytical model than NRZ for 

modeling the SONAbeam 622-M gear’s BER performance, due to its assumption of full 

bit-window data bits, and non-coherent data detection in the actual hardware. 

Probability of error for OOK-coded electrical data is given by:14

1

2 erfc

2 E

z P

⎛ = ⋅ ⎜

⎜

⎝ ⎠

⎞

⎟

⎟ (2) 

A theoretical 10-9 BER is achieved for approximately a 15.6 dB data signal to noise 

power ratio. Probability of error for OOK-coded optical data, detected with a photodiode 

(see Appendix B), is given by: 

1 1

2 22 E

z P erfc

⎛ ⎞ = ⎜ ⎟

⎝ ⎠

 (3)

 A theoretical 10-9 BER is achieved for approximately a 21.6 dB signal to noise power 

ratio. This BER performance level applies only in the absence of atmospheric turbulence, 

which only increases the effective implementation loss of hardware measured against 

theoretical OOK-coded BER performance curves. Such OOK-coded or IM/DD data has 

 

13 R. Ziemer, W. Tranter, Principles of Communications, Systems, Modulation, and Noise, Houghton 

Mifflin Co., Boston, 1976, p. 315. 

14 IRIG Standard 106-04, Part I, Appendix C, p. C-1 (p. 356 of 495.) 

http://www.ntia.doc.gov/osmhome/106-04.pdf , approved for public release, unlimited distribution. 

39
ECT – Phase 4 

 

also been known as unipolar Non Return to Zero Level, NRZ-Level, and NRZ Change 

encoded data when discussed in IRIG telemetry standards.15

The data signal to noise power ratio in either case (i.e., for either NRZ or OOK) is 

z which is defined as 

0

S

z

N

⋅τ = (4) 

where S is the total signal power in Watts, τ is the bit period in seconds, and No is the 

noise power spectral density in Watts/Hz. 

The inverse of the bit period is the bit rate bandwidth. That is, 

1 R

τ

= (5) 

Re-writing Eqn. 4, the physical interpretation becomes the ratio of the total signal power 

to the total noise power, i.e., the signal to noise ratio, as measured in the bit rate 

bandwidth. That is to say: 

0

b

o

S E

z

NR N = = ⋅ (6) 

Provided that average signal-to-noise ratio, denoted by <SNR>, is defined in exactly the 

bit rate bandwidth, <Eb/No> becomes exactly equal to the <SNR>. The key point is that 

the signal to noise ratio is not what determines the BER performance, unless proper 

assumptions are made relative to the bandwidth over which the noise power spectral 

density is assumed to be integrated. 

In the presence of atmospheric turbulence, the probability of error (BER) is considered to 

be a conditional probability that must be averaged over the probability density function 

(PDF) of a random signal s to determine the unconditional BER. This action leads to the 

expression: 

0

1 Pr( ) ( )erfc 2 22 Is SNR E ps ∞ ⎛ < > = ⎜

⎜

⎝ ⎠ ∫ ds

⎞

⎟

⎟ (7) 

where <SNR> is the average signal-to-noise ratio and ( ) I p s is the PDF of the normalized 

signal (unit mean). 

 

15 M. A. Al-Habash, L. C. Andrews, and R. L. Phillips, “Mathematical model for the irradiance PDF of a 

laser beam propagating through turbulent media,” Opt. Eng. 40, 1554-1562 (2001). 

40
ECT – Phase 4 

 

Rather than using the traditional log-normal PDF, which is valid only under assumptions 

of weak turbulence, we find that the gamma-gamma PDF is more accurate under both 

weak and strong turbulence conditions. Hence, in the analysis, we use the gammagamma PDF defined by13: 

( ) ( )/2 2( ) ( )/2 1 ( ) 2 , 0 ()() I p s s K s s

α β α β α β

αβ αβ α β

+ + − = − Γ Γ

>

−

 (8) 

where parameters α and β are related to the reciprocals of the large-scale and small-scale 

irradiance fluctuations, respectively, of the random signal. In particular, the scintillation 

index of the irradiance fluctuations takes the form: 

22 2

ln 0 0 ln 0 exp ( , , ) ( , ) 1, Ix y σσ σ = + ⎡ ⎤ lLD lD ⎣ ⎦ (9) 

where D is the receiver aperture diameter, and where we define: 

2 2

ln 0 0 ln 0

1 ,

exp ( , , ) 1 exp ( , ) 1 x y lLD l D

α β

σ σ

= = ⎡ ⎤⎡ − − ⎣ ⎦⎣

1 . ⎤

⎦

 (10) 

Expressions for the large-scale and small-scale irradiance fluctuations are from published 

equations.16

The implementation loss measured relative to the NRZ theoretical curve is what 

determines the absolute quality of any particular set of hardware, as well as the true 

performance impact introduced by an assortment of degradations ranging from perhaps 

the timing uncertainty in particular bit synchronizers to, as is the topic of interest in this 

paper, the BER effects of optical scintillation versus aperture diameter size. For applying 

the results to real hardware, however, while accounting for real hardware limitations, the 

OOK theoretical curve is often more applicable, such as is the case for the measurements 

reported herein. 

2.7.5 Detailed Results

Measured and theoretical values of the BER for a receiver aperture of 1.25 inches are 

shown in Figure 2-29 for one-minute averages. The rather meaningless scatter-diagram of 

Figure 2-29 shows the need for increasing the averaging time in order to make 

 

16 L. C. Andrews, R. L. Phillips, and C. Y. Hopen, Laser Beam Scintillation with Applications (SPIE Press, 

Bellingham, WA (2001). 

41
ECT – Phase 4 

 

meaningful comparisons between theory and measured data. We therefore performed 

averages of all quantities over a five-minute period and plotted the results in Figure 2-30. 

In Figure 2-30, we also included measured data over the time period from 1:45 PM to 

3:00 PM with corresponding predicted theoretical values. During this latter time period, 

however, we often lost lock on the BER instrumentation and most of the measured data 

was at either high BER values or nearly zero. We believe taking data over longer time 

periods (5-10 min.) would eliminate most of the remaining erratic behavior observed in 

comparing theoretical predictions with measured data. 

16 18 20 22 24 26 28 30 32 34

<SNR> (dB)

10-5

10-4

10-3

10-2

10-1

2

3

4

6

2

3

4

6

2

3

4

6

2

3

4

6

<BER>

Noise power = 5.5 nW

Rx Diameter = 1.25 in

June 3, 2005 

Measured

Theory

Time of Day (1:00 PM--1:40 PM)

1 minute averages

Figure 2-29 1-min. Avg. BER Vs. SNR

42
ECT – Phase 4 

 

23 24 25 26 27 28 29 30 31

<SNR> (dB)

10-5

10-4

10-3

10-2

10-1

2

3

4

6

2

3

4

6

2

3

4

6

2

3

4

6

<BER>

Noise power = 5.5 nW

Rx Diameter = 1.25 in

June 3, 2005 

Measured (1:00--1:40 PM)

Theory (1:00--1:40 PM)

Measured (1:45--3:00 PM)

Theory (1:45--3:00 PM)

Time of Day (1:00 PM--3:00 PM) 5 minute averages

Figure 2-30 5-min. Avg. BER Vs. SNR

For both Figures 2-29 and 2-30, to compare theoretical predicted results with these 

measured quantities, it was necessary to first calculate the mean noise power at the 

receiver. This back-to-back measurement was done under laboratory conditions in the 

absence of atmospheric effects and found to be 5.5 nW for Transmitter Power Level 7 

(highest level). Transmitter Power Level 7 for the fSONA transmitter was chosen 

specifically since it had the best extinction ratio (best eye diagram) in contrast to Power 

Levels 1 through 6, thereby reducing the introduction of hardware effects in accurately 

measuring the BER performance impacts of atmospheric turbulence. Using this value for 

the mean noise power, and the measured average signal power at the receiver, the 

resulting theoretical BER was calculated using Eq. (7) and also shown in Figures 2-29 

and 2-30. The parameters (9) of the gamma-gamma distribution (8) were based on pathaveraged values of Cn

2

, calculated inner scale values over the period of the experiment, 

and the strong fluctuation scintillation theory.17

 

17 L. C. Andrews, R. L. Phillips, and C. Y. Hopen, Laser Beam Scintillation with Applications (SPIE Press, 

Bellingham, WA (2001). 

43
ECT – Phase 4 

 

The data of Figures 2-29 and 2-30 show that we are still at a preliminary stage in 

validating published theory for predictive purposes, and that considerably more collected 

data are required to complete the validation. Considering that BER is a predictive tool 

for estimating average performance in an otherwise random environment, the need for 

more data is not surprising. 

Figure 2-31 shows measured BER and error count data versus receive aperture diameters 

of 2-inches, 3-inches, and 8-inches (full-aperture) over a 1 km link. For aperture 

diameters of 2-inches, the measured BER is seen to have often clustered around 10-3, 

showing only occasional improvements to 10-7 to 10-10. The full aperture (8-inches), 

when checked around 1:55 PM, provided essentially 10-12 or better (error-free) BER with 

only a few instances of 10-5 BER. However, for receive apertures of 3-inches measured 

around 3:00 PM, BER performance ranges from 10-9 to 10-12 or better (i.e., error-free.) 

The data therefore indicate that over a 1 km terrestrial link, a receive aperture diameter of 

3-inches, or larger, is probably the minimum that should be used to achieve good or 

adequate performance. 

BER & Error Count

SLF 23 may 05; 1 Km Link

1.E-13

1.E-12

1.E-11

1.E-10

1.E-09

1.E-08

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

12:00 PM 12:28 PM 12:57 PM 1:26 PM 1:55 PM 2:24 PM 2:52 PM

Time

BER

1.E-01

1.E+00

1.E+01

1.E+02

1.E+03

1.E+04

1.E+05

1.E+06

1.E+07

1.E+08

1.E+09

Error Count

Error Ratio

Error Count

Rx: 2" Aperture @ 7o'c

Tx: L7 @ 1 O'clock

Rx: Full Aperture

Tx: L7 @ 1 O'clock

Rx: 2" Aperture @ 7 o'c

Tx: L7 @ 1 O'clock

Rx: 3" Aperture @ 7 o'c

Tx: L7 @ 1 O'clock

Rx: Full Aperture

Tx: L7 @ 11 O'clock

Figure 2-31 BER & Error Count Vs. Time of Day & Aperature Dia.

44
ECT – Phase 4 

 

Although the 3-inch minimum diameter for achieving good BER performance over a 1 

km link appears to be the minimum diameter that should be employed, there are times 

when a smaller diameter aperture can nonetheless provide surprisingly good 

performance, lasting through appreciable periods of ‘good seeing.’ Figure 2-32 shows 

measured BER data for 1.0-inch and 1.25 inch apertures, respectively, measured over a 1 

km long link. For the 1-inch diameter receive aperture, a BER of around 10-2 to 10-3 is as 

good as could be achieved. Yet, for a 1.25-inch diameter receive aperture, BER 

performance often achieved 10-6 to 10-12 to error free. These data also show that 

increasing aperture averaging through increasing receive aperture diameters only slightly 

can be a major factor in determining, or at the very least improving rather dramatically, 

the BER performance of a free-space optical link. Aperture averaging can clearly work to 

improve measured BER performance dramatically for only very slight increases in 

receive aperture diameter under appropriate atmospheric turbulence conditions. 

The variations of the refractive-index structure parameter, , must also be considered, 

in addition to the variations in the receive aperture diameter for completeness, less the 

importance of only slight differences in receiver aperture diameter become overstated. 

Figure 2-33 shows variation for June 3

2 Cn

2 Cn

rd, applicable for the measured data shown in 

Figures 2-27 through 2-30 & 2-32 vs. measured BER. As one would expect, the peak of 

 occurs around local solar noon, perhaps delayed slightly (10-15 minutes or so) at 

which time the scintillation is near its peak diurnal value. It then decreases rather rapidly 

for approximately an hour, as the sun descends toward the western horizon, before 

plateauing to nearly a constant value. 

2 Cn

3 June 05 , 1Km, Bit Er r or Ra t io

Tx Le ve l 7 ; Rx &Tx 1 o' c lock posit i on

1E-12

1E-11

1E-10

1E-09

1E-08

1E-07

1E-06

0.0000

1

0.0001

0.001

0.01

0.1

1

10:48 AM 11:16 AM 11:45 AM 12:14 PM 12:43 PM 1:12 PM 1:40 PM 2:09 PM 2:38 PM 3:07 PM 3:36 PM

T i me

Error Ratio

Rx: 1.0" Aperture Rx: 1.25" Aperture

Error Free

Figure 2-32 BER Vs. Time of Day @ 1.0 & 1.25 Aperture Dia.

45
ECT – Phase 4 

 

BER & Cn^2

SLF 1 Km link

1E-12

1E-11

1E-10

1E-09

1E-08

1E-07

1E-06

1E-05

0.0001

0.001

0.01

0.1

1

10:48 AM 11:16 AM 11:45 AM 12:14 PM 12:43 PM 1:12 PM 1:40 PM 2:09 PM 2:38 PM 3:07 PM 3:36 PM

Time

BER

0.0E+00

5.0E-14

1.0E-13

1.5E-13

2.0E-13

2.5E-13

3.0E-13

Cn^2

Error Ratio

Cn^2 Corr

Rx: 1.0" Aperture Rx: 1.25" Aperture

Error Count 

Figure 2-33 BER & Cn

2

 Values Vs. Time of Day @ 1.0 & 1.25 Aperture Dia.

2.7.6 Conclusions and Recommendations For Further Research

Results of FSO scintillation tests conducted at the SLF runway at KSC have been 

presented. The absolute accuracy of the theoretical predictions of BER performance 

versus measured BER for specific receiver aperture masks are still inconclusive based on 

the limited data obtained during these experiments. The theory matches much of the 

measured data quite well but some of the measured data does not fall where the theory 

predicts. Additional experiments are necessary to make more definitive statements about 

the subtle differences between our theory and measured results. Longer term data 

collection would enable improving the accuracy of the theory through better 

understanding the limitations of the presently-developed predictive equations. 

Nonetheless, the use of the theory as published appears adequate to enable a priori

performance estimation of FSO link performance within the unique KSC environment. 

The fundamental characteristic of improving BER through increasing receive aperture 

diameter, though, is clear. Differences in aperture averaging through increasing receiver 

aperture diameters only slightly can sometimes greatly improve measured BER 

46
ECT – Phase 4 

 

performance. Additionally, there are rather long moments of ‘good seeing’ during which 

times surprisingly good BER link performance can be achieved despite the use of rather 

small receiver aperture diameters. 

More research is needed to understand better the limitations and benefits of aperture 

averaging to achieve better BER performance for terrestrial point-to-point data links. 

The minimum aperture size that should be considered for implementing very short FSO 

links at KSC is 10 cm, and aperture diameters of 32 cm, or larger, should be considered 

as being the minimum practical diameters that should be deployed over paths of 1 km or 

longer within the hot Florida locale of KSC. 

In addition to the receiver aperture averaging advantage reported in this paper, 

transmitter aperture averaging effects also need to be investigated in the course of future 

research, time permitting. 

47
ECT – Phase 4 

 

3.0

48
ECT – Phase 4 

 

EXTENDED RANGE WIFI

3.1 BACKGROUND 

Operation of Extended-Range (E-R) Wi-Fi equipment can be accomplished using 

licensed or unlicensed frequency bands. Acquiring a license to operate such equipment 

can be time-consuming and costly. After considering the project’s budget and timeline, it 

was decided to utilize an unlicensed frequency band, to expedite testing, while following 

NASA Spectrum Management rules. Part-15 authorized unlicensed equipment could be 

tested without the need for NTIA Federal Frequency approvals, and was the choice made 

to expedite testing. 

Hence, our E-R Wi-Fi testing under the ECT project was conducted around the 

DragonWave AirPair 100 with equipment operating at the unlicensed 24 GHz ISM 

(Industrial, Scientific, Medical) FCC-allocated frequency band. The DragonWave 

system was the first and only system available that would operate at the selected 

frequency band at the time that this equipment was procured, although additional vendors 

are scheduled to have started releasing competing equipment subsequent to the start of 

our testing. 

3.2 BASIC E-R WI-FI THEORY 

Wi-Fi (Wireless Fidelity, i.e., wireless Ethernet) is intended for use over short 

communication ranges and was investigated and its measured performance was discussed 

previously in the prior years’ final reports. It is not the focus of activity in this year’s 

report. 

Nonetheless, Wi-Fi provides excellent wireless Internet connectivity over distances up to 

a few hundred meters for laptops and related assorted wireless networked appliances 

(e.g., shared printers, print servers, cameras, server hard-drive storage banks, speakers, 

scanners, etc.) Although certainly useful over short ranges, Wi-Fi does not provide 

connectivity over the longer ranges needed for implementing the future Range vision of 

First Mile/Last Mile connectivity over longer, or extended-range distances. 

Subsequently, the focus for this year was on achieving longer range communication, with 

essentially a Wi-Fi compatible wireless link, through utilizing Extended-Range (E-R) 

Wi-Fi. 

Most E-R Wi-Fi communication equipment operates fundamentally through providing an 

Ethernet interface at two points, with an interconnecting microwave or millimeter wave 

communication wireless or radio frequency link being used for providing virtual wired 

connectivity between the two points. Hence, existing E-R Wi-Fi tends to be point-topoint radio links, although they are links that behave much like shorter-distance wired 

local area networks (LANs) implemented with traditional Wi-Fi. 

49
ECT – Phase 4 

 

For such E-R Wi-Fi systems, microwave high-gain dish antennas are used, typically with 

beamwidths of less than 5 degrees, with higher-gain antennas of course having smaller 

beamwidths. Transmit powers of a few milliwatts up to hundreds of milliwatts are used 

by authorized unlicensed systems, with higher transmit powers of Watts or tens of Watts 

being reserved for E-R Wi-Fi systems requiring FCC or NTIA licensing. 

The advantage of such systems, whether permitted as licensed or unlicensed, is that 

effective isotropic radiated power (EIRP) is increased through using the high-gain dish 

antennas, and frequency re-use is likewise possible within a general geographic area 

through taking advantage of sectoral or otherwise geometry-restricting antenna radiation 

patterns. The use of common high-gain antennas, used for both transmit and receive 

functions, works to increase received signal levels, while likewise also reducing the 

amount of transmitter power required to achieve high fidelity low Bit Error Rate (BER) 

data links. 

E-R Wi-Fi systems are not the only way to provide longer range Wi-Fi compatible 

operation. Alternative systems are under development by industry leaders as well, for 

providing wide area network (WAN) Ethernet communications, instead of only providing 

point-to-point communication links, such as used for E-R Wi-Fi. These systems include 

EvDO (Evolution- Data Only) and Wi-Max, typically used for providing wireless 

Internet connectivity over wide areas of major metropolitan areas. Wi-Max will be 

investigated next year. 

3.3 CHOICE OF E-R WI-FI FOR TESTING 

Initially, an E-R Wi-Fi system sold by Mobicomm in the Netherlands was investigated. 

It was available in a variety of configurations, operating on one of a range of existing 

frequency allocations usually reserved for PCS or cell phone licensed operation within 

the United States. However, there were two major issues with procuring and testing this 

system. First, Mobicomm ceased production of their first designs, and entered a redesign activity, to overcome design deficiencies in their initially sold designs, prior to the 

receipt of project funding that could enable the procurement of an E-R Wi-Fi system for 

testing. Second, through virtue of operating on FCC-authorized frequencies reserved for 

cell phone transmissions within the US, obtaining permission from the NASA Spectrum 

Manager, and from NTIA, while also coordinating with the FCC, appeared to be a largely 

impossible task, at least within the time constraints of desiring to test an E-R Wi-Fi 

system this fiscal year. 

Fortunately, the FCC authorized a new unlicensed ISM band at 24 GHz for the purpose 

of providing spectrum for achieving E-R Wi-Fi operation within the US. DragonWave, a 

small Canadian wireless hardware company provider outside of Ottawa, responded 

through quickly re-designing and releasing a modified version of their system requiring 

FCC licensing but which could operate on the newly authorized 24 GHz unlicensed ISM 

band. This was the system that was procured for testing. 

50
ECT – Phase 4 

 

3.4 TEST DESCRIPTION 

Initial tests were to become familiar with the system and to evaluate its performance at a 

very short distance (approximately 60 meters). Later tests were to evaluate performance 

at increasing link distances (1, 1.5, 2.0, and 2.5 miles). Weather testing was not 

accomplished in this phase. 

3.5 TEST OBJECTIVES 

The Extended Rage Wi-Fi test objectives were as follows: 

 Evaluate COTS Extended-Range Wi-Fi equipment for possible future use at KSC 

 Identify any fundamental shortcomings that must be mitigated in commercial 

Extended-Range Wi-Fi communication technologies prior to integrating this 

technology into future range architectures. 

3.6 TEST SETUP 

The test setup utilized when evaluating the Dragonwave E-R Wi-Fi AirPair 100 

equipment was similar in all test cases. The primary difference between tests was just the 

distance between the two ends of the system. Initially, the system was tested at a very 

short distance (approximately 60 meters). This was done primarily to become familiar 

with the hardware, the software, and to practice aligning the antennas, while doing initial 

setup testing in the EDL back parking lot. The system was then moved to Schwartz Road 

to perform tests over greater distances. 

The basic setup was to place the two AirPair 100 units a fixed distance apart and 

establish a link. Initial alignment was usually accomplished using a 12X power rifle 

scope borrowed from the FSO testing described previously, attached to a frame housing 

that was modified to permit attachment of the scope in addition to providing a mounting 

bracket for the RF head of the AirPair 100 unit. 

 

Once an initial link was established, the pointing of link antennas was refined and 

optimized using the Web Interface on a laptop computer to provide feedback of the 

received signal level reading of the AirPair 100 system. Fine adjustment was 

accomplished using jacking screws on both azimuth and elevation lever arms. 

WSTTCP (a Windows socket port of the BSD TTCP, i.e., of the Unix BSD Test TCP, 

software) was used to test data traffic throughput performance over the wireless link. 

This software runs on the laptops at each end of the wireless network. One laptop was 

configured to transmit test data and the other to receive. The receiver reports the results 

of the test back to the transmitter for completion purposes via the Ethernet connection. 

Tests were executed using two different data buffer sizes. The results of each test 

51
ECT – Phase 4 

 

reported the effective data throughput provided by the wireless network enabled by the 

AirPair 100 system. 

The primary independent variable for all tests was link distance. A summary of test 

locations and distances is included in the following table. Specific details about each test 

location are included in the following sections. The AirPair 100 system, test equipment, 

and software are described in later sections. 

Table 3-1 Test Locations 

 

No. Location One-Way Distance 

1 Schwartz Road 1.0 mile 

2 Schwartz Road 1.5 miles 

3 Schwartz Road 2.0 miles 

4 Schwartz Road 2.5 miles 

5 Shuttle Landing Facility 3.2 miles 

3.6.1 Schwartz Road Test Setup

Schwartz Road is a remote East-West road at KSC that runs relatively straight for 2.7 

miles. Most of the testing was performed at this location. Trailers were positioned off 

to the side of the road at various separation distances. Initial testing was performed at 1.0 

mile separation between trailers. This was followed by tests at 1.5, 2.0, and 2.5 miles. 

The west trailer remained fixed during all tests. 

Trailer #2 was positioned in the turn on the west end of Schwartz Road. It remained 

stationary during all tests. Figure 3-1 shows Trailer #2 parked on the west end of 

Schwartz road during a test. The AirPair 100 unit is mounted on the pole on the left. 

Trailer #1 was repositioned to the east side on Schwartz Road as needed to set the desired 

link testing distance. Figure 3-2 shows Trailer #1 parked off to the side of Schwartz road 

during one of the tests. The AirPair 100 unit is mounted on the pole to the right and is 

focused up Schwartz Road to the west. 

52
ECT – Phase 4 

 

Figure 3-1 AirPair 100 On Trailer #2 At West End Of Schwartz Rd. 

Figure 3-2 AirPair 100 On Trailer #1 At East End Of Schwartz Rd. 

53
ECT – Phase 4 

 

3.6.2 Shuttle Landing Facility (SLF) Test Setup 

The trailers with the E-R Wi-Fi equipment were placed as far apart as possible at the 

SLF. Fortuitously, the runway length plus the paved overruns at each end provide a 

separation distance of 3.2 miles. As the goal was to test performance at a distance of 3 

miles or slightly greater over a controlled surface roughness path, the SLF provided an 

extremely uniform path at exactly the distance desired, over which to conduct testing. 

As expected, for the low fixed height of the antennas at only 2 meters above the concrete, 

the predicted Fresnel Zone degradation of received signal strengths kept the link from 

performing well while testing at this distance, despite the use of otherwise adequate 

antenna gains and transmitter powers as predicted for closing the link. This result 

confirmed that the expected Fresnel Zone degradation exists at distances of 3.2 miles 

with E-R Wi-Fi antennas mounted at a 2 meter height, and that for operation at this 

distance, positioning of antennas at greater Height Above Average Terrain (HAAT) is 

recommended. 

3.7 TEST EQUIPMENT AND SOFTWARE 

Key E-R Wi-Fi test hardware included the following: 

• DragonWave AirPair 100 Modem, Radio, and Antenna 

• Laptop computer for interfacing with the Modem 

In addition to the above hardware, one software utility was instrumental in testing data 

throughput: 

• WSTTCP (a Windows socket port of the BSD TTCP, i.e., of the Unix BSD Test 

TCP, software) to transfer data through a TCP data flow between the two laptops 

WSTTCP Ref.s: http://www.pcausa.com/Utilities/pcattcp.htm and 

http://www.winsite.com/bin/Info?5896 

3.7.1 DragonWave AirPair 100

The DragonWave AirPair 100 was the primary component under test. The factory units 

were modified as shown in Figure 3-3 to include a riflescope attachment. The modem 

shown in Figure 3-4 was attached to the same mounting pole. Specifications for the units 

are summarized in Table 3-2. A pair of AirPair 100 units were purchased around 3/1/05 

under the ECT task order (#00087). 

54
ECT – Phase 4 

 

Included for the purchase price were the following system components: 

• (2) AirPair100 Outdoor Radios 

• (2) AirPair100 Modems with 30 cm Antennas 

• (2) Power supplies 

• (2) Power + Ethernet Cables 

• (2) IF Cables (Modem – Radio) 

• (2) Mounting Brackets 

• Link Budget utility 

• Factory training for project personnel 

Figure 3-3 Modified AirPair 100 Radio with 30cm Antenna & Added 

Riflescope 

55
ECT – Phase 4 

 

Figure 3-4 AirPair 100 Outdoor Modem 

Factory training was included with the purchase of the AirPair 100. Training took place 

in Ottawa, Ontario on 7/14/05. ASRC employees Dr. Gary Bastin, Bill Harris, and 

José Marín attended. 

The units were shipped with a cable assembly that connects to the modem and which 

breaks out three different interfaces: power, data, and management. The power cable 

(black) has a 5-pin DIN connector that mates to the power supply provided with the unit. 

The data cable (blue) provides the 100BaseT Ethernet interface. The management cable 

(gray) provides the 10BaseT Ethernet interface. The cable assembly is shown separately 

in Figure 3-5 and connected to the Dragonwave unit in Figure 3-6. 

During normal operation, the units can be managed from a Simple Network Management 

Protocol (SNMP) Manager. Connectivity to the SNMP Agent can be achieved via the 

data network (in-band) or via the management network (out-of-band). Selection of the 

network in use for SNMP traffic is user-selectable during system configuration. 

56
ECT – Phase 4 

 

Table 3-2 AirPair 100 Specifications 

Manufacturer DragonWave Inc. 

600-411 Legget Drive 

Ottawa, Ontario, 

Canada K2K 3C9 

Model AirPair 100-UL 24 GHz 

Data rate 100 Mbps full duplex performance 

Distance Up to 5 miles 

Frequency Range 24.05 – 24.25 GHz 

Antenna Diameter 30 cm 

Antenna Gain 35.3 dBi 

Antenna Beamwidth 2.6° 

Modulation 16 QAM 

RF Power +3 dBm 

Data Interface 100BaseT 

Data Interface Connector RJ-45 

Management Interface (Out-of-band) 10BaseT 

Management Interface Connector RJ-45 

Local Management Interface RS-232 

Local Management Interface Connector DB-9 

Voltage (110V adapter supplied) 48 vdc 

Environment Operating Temp -40°F to +122°F 

 Max Operating wind 70 mph (Antenna) 

Warranty 1 year 

Serial Numbers AirPair 100 #1 DW320759 

 Radio #1 410141 

 AirPair 100 #2 DW320720 

 Radio #2 410590 

Software Loaded omni_3.4.5.hex 

Configuration (and management) of the system can be performed via the Web Interface 

(available in-band or out-of-band), or via the Command Line Interface (CLI) which is 

available via telnet (in-band or out-of-band) or via the serial interface (RS-232). Test 

configuration parameters are listed in Table 3-4. 

57
ECT – Phase 4 

 

 Figure 3-5 Power + Ethernet Cable 

Figure 3-6 Pole Mount with AirPair 100 Modem, Radio, and Antenna 

58
ECT – Phase 4 

 

Table 3-3 AirPair 100 Test Configuration Parameters 

East End (#1) West End (#2) 

Software Loaded omni_3.4.5.hex omni_3.4.5.hex 

Super User name dw1 dw2 

Super User password dwx dwx 

IP address 128.217.108.180 128.217.108.181 

Subnet Mask 255.255.0.0 255.255.0.0 

Radio Band un24 un24 

Frequency Bank Go Return 

Programmed Freq UNL1 (Tx=24080 Rx=24160) UNL’1 (Tx=24160 Rx=24080) 

Antenna Diameter 30 cm 30 cm 

Transmit Power 3 dB 3 dB 

Antenna’s height +- 75 inches +- 75 inches 

Laptop IP address 128.217.108.175 128.217.108.174 

Auto negotiation Disabled/Enabled Disabled/Enabled 

3.7.2 Laptop

A pair of Gateway laptop computers, purchased in an earlier project year and depicted in 

Figure 3-7, were used to support E-R Wi-Fi testing. The configuration and management 

functions performed on the AirPair 100 system were accessible via Internet Explorer, 

telnet, and Command Prompt (i.e., no special software was required to be loaded to 

perform these tasks in addition to the Windows Operating System) on the laptops. The 

link budget software tool provided by DragonWave is simply a Microsoft Excel 

spreadsheet, built-in to the normal MS Office tools. To perform data throughput testing, 

each laptop was also loaded with the WSTTCP utility, developed as part of the Open 

Source software initiative among the Internet community. Both of these utilities are 

discussed in more detail in a later section. 

3.7.3 DragonWave AirPair 100 Controller Software

The AirPair 100 can be configured and controlled using the SNMP Manager, Command 

Line Interface (CLI), or Web Interface. 

The SNMP Manager option was not used since that utility is not readily available in the 

Range lab. Testing via this option will need to be performed among later tests, as part of 

the final networking compatibility testing, prior to “going operational” with this 

hardware. 

 

59
ECT – Phase 4 

 

Figure 3-7 Laptop connected to the AirPair 100 Modem 

The CLI is accessible three different ways: terminal emulator (RS-232), telnet 

(Ethernet), or via a custom utility running on a Personal Digital Assistant (PDA) (RS232). The PDA option was not used since a PDA with the required operating system 

version was not readily available. The terminal emulator included with the Laptop’s 

operating system (HyperTerminal) was used to perform initial configuration selection of 

parameters for the AirPair 100 Modems. The telnet utility included with the Laptop’s 

operating system was used to test the interface. This interface is similar to using 

HyperTerminal. 

Using the CLI was difficult since the user is expected to be knowledgeable with the 

complete command set. Also, this mode requires lots of keyboard use which can be 

inconvenient when operating the system in the field during field testing. 

Figures 3-8 and 3-9 provide screen capture images of two “get” commands (get status of 

led’s and get hardware revision), and also gives a good feel of the operator actions 

required for using this mode: 

60
ECT – Phase 4 

 

Figure 3-8 CLI screen capture (Laptop) 

Figure 3-9 Web Interface – General Radio Information Page 

61
ECT – Phase 4 

 

The Web Interface is much easier to use and is more user friendly. In addition, it can be 

configured to poll the modem for the settings relevant to the system alignment at a 

configurable rate of seconds. The Web Interface is hosted by the software in the Modem, 

thereby making it accessible from the Internet Explorer software included natively with 

the Laptop’s operating system. Figure 3-9 shows a screen capture of the General Radio 

Information page of the Web Interface. The left side of the page shows the settings that 

are polled to simplify operation of the system while in the field. 

3.7.4 DragonWave Link Tool

The AirPair 100 system included a software utility to calculate the link budget. This tool 

enables the user to easily calculate the expected Received Signal Level (RSL) for a given 

configuration. By knowing the expected operating performance values, the user thus 

knows immediately upon establishing a link whether everything is operating as it should. 

When measured link parameters are not as predicted, then something needs adjusting, to 

achieve full system performance. Through using this prediction tool, the elimination of 

improperly configured or improperly performing links is achieved, reducing the need to 

return to the field to re-adjust a link. 

Figure 3-10 shows a screen capture of the utility. This example shows that when the two 

ends of the system are installed one mile apart from each other, the expected RSL is -

52.10 dBm. During alignment of the system, the user strives to achieve an RSL within 3 

dBm of this calculated RSL. Optimum RSL values for the distances tested are shown in 

Table 3-4. 

Table 3-4 Optimum RSL Values Vs Distances 

Distance (Mi) Optimum RSL (dBm) 

1.0 -52.10 

1.5 -55.75 

2.0 -58.39 

2.5 -60.46 

3.0 -62.18 

Other optimum parameters monitored during setup are shown in Table 3-5. 

Table 3-5 Optimum Parameters 

Parameter Optimum Range 

Eb/No >20.0 

Stress 3-5% 

62
ECT – Phase 4 

 

Figure 3-10 LinkTool utility 

3.7.5 Throughput Testing

Throughput testing was performed with the help of the “WSTTCP” utility. 

WSTTCP Ref.s: 

http://www.pcausa.com/Utilities/pcattcp.htm and 

http://www.winsite.com/bin/Info?5896

WSTTCP is a WINSOCK (i.e., a Windows socket) port of the BSD TTCP, i.e., of the 

Unix BSD Test TCP, software. It is used to transfer data through a TCP data flow 

between two computers. 

63
ECT – Phase 4 

 

WSTTCP was loaded on both laptops. During each WSTTCP run, one laptop was 

configured to act as the transmitter and the other as the receiver. Most of the WSTTCP 

settings were left at default values with two exceptions: socket port number and number 

of source buffers written to network during each test. 

The socket port number was changed to 5002 (from 5001). This change was required as 

the two laptops’ Norton Symantec Anti-Virus software would not allow port 5001 to be 

used for data transfer purposes. 

Likewise, the number of source buffers written over the network during each test was left 

at the default (2048) for half the tests and modified to 10,000 for the other half, to 

determine if the size of buffers transferred would have any impact on data throughput 

performance. During each test, the buffers contained 8,192 bytes of data. In effect, some 

tests passed 16,777,216 bytes of data while the others passed 81,920,000 bytes. 

At the transmitter side of the test, the running WSTTPC utility needs to know the IP 

Address of the receiving laptop. This parameter was configured to 128.217.108.174. 

WSTTCP is commanded to run from the command line (Command Prompt). The 

receiving laptop was configured with the following command: 

 WSTTCP –r –p5002 

The transmitting laptop was configured with the following commands: 

 WSTTCP –t –p5002 128.217.108.174 

 WSTTCP –t –p5002 –n10000 128.217.108.174 

The WSTTCP utility displays throughput statistics indicating the quality of the link from 

end to end after completing each run. 

3.8 TEST RESULTS 

3.8.1 General

E-R Wi-Fi testing started at the Engineering Development Lab (EDL) where the AirPair 

100 systems were installed on the trailers and powered-up for the first time. The primary 

test objective at this location was setup, initialization, checkout, and familiarization, prior 

to testing at a remote site where there would be few resources to debug problems. 

The second stage of testing took place at Schwartz Road. At this location, the system 

was tested two different times. This first time it was tested at distances of 1.0, 1.5, 2.0, 

and 2.5 miles apart. After completing these tests, the test engineers attended a vendorprovided training course. Testing resumed shortly after returning from the training. This 

time, the system was tested at distances of 1.0, 2.0, and 2.5 miles apart. The primary test 

objective at this Schwartz Road location was making data throughput measurements over 

64
ECT – Phase 4 

 

the wireless network provided by the AirPair 100 system. The 24 GHz absorbing rough 

terrain vegetation alongside Schwartz Road largely avoided the deleterious effects of 

Fresnel Zone degradation during these tests. 

As not all fielded sites will be operating over absorptive materials, the effects of Fresnel 

Zone degradation due to destructive interference between direct and reflected signals off 

the ground was desired to be verified. Published rules-of-thumb nomograms indicated 

that such degradation would likely occur around 3.0 miles, or slightly greater, provided a 

uniformly consistent and largely non-disappative surface was beneath the link, for the 

height above ground of 2 meters for the mounted microwave dish antennas. Hence, the 

third stage of the testing took place at the Shuttle Landing Facility (SLF), as this would 

enable determining what the worst case degradation for a very uniform surface beneath 

the propagating path would be. At this location the primary objective was to push the 

distance limit of the system to slightly more than 3.0 miles, and see if link degradation 

above what the previously mentioned link tool predicted, would occur. It was expected 

to experience difficulties obtaining a link with a signal quality capable of providing a 

reliable path for a successful data throughput test, despite the use of adequate antenna 

gain and transmitter power and receiver sensitivity to otherwise close the link. The 

maximum capable distance at the SLF is 3.2 miles of separation. It was decided to push 

the equipment to the full 3.2 miles. 

After reviewing the data collected through the first 3 stages, DragonWave field support 

was contacted and helped mitigate an obvious shortcoming that we noticed in the 

throughput performance for our system (e.g., data throughput was never achieving higher 

than 8.6 Mbps). It was noted that our AirPair 100 system was improperly configured to 

keep the network interface from automatically negotiating the network’s speed 

(improperly setting operation at 10Mbps vs. 100Mbps). This setting kept the test laptop 

from operating at its full speed of 100Mbps. A fourth set of tests was added to the testing 

to enable testing throughput while simultaneously allowing the system to negotiate the 

network’s speed automatically, and thereby achieve the highest data rate throughput 

performance possible with the equipment. Table 3-6 summarizes the types of tests. 

Table 3-6 Summary of Test Locations & Objectives 

Location Test Objectives 

EDL Setup, initialization, checkout, and familiarization 

Schwartz Road Familiarization and data throughput 

SLF Push the distance limitation 

Schwartz Road Test data throughout with Auto Negotiate Enabled 

3.8.2 Results Summary

 

E-R Wi-Fi testing was conducted from May 2005 through September 2005. The first 

phase (setup, initialization, checkout, and familiarization) was performed at the EDL 

parking lot at a distance shorter than what the system was designed to operate 

65
ECT – Phase 4 

 

(approximately 60 meters). During this phase DragonWave’s tech support was very 

helpful and was readily available to address the initial issues and noted concerns. During 

this phase, no data throughput testing was performed, as the topic of interest was simply 

hardware familiarization and proper usage checkout. 

The second phase was conducted at Schwarz Road from July 2005 to mid-August 2005. 

Successful links were established at distances of 1.0, 1.5, 2.0, and 2.5 miles. The 

mounting hardware used for the antennas proved to be overly difficult to use during 

alignment. Once aligned, this hardware secures the antenna in place as it was designed to 

do. Unfortunately, this hardware is not designed for quickly aligning test setups 

regularly, but rather for rarely aligning fixed installations. We added a 12x power 

riflescope mount to expedite quick repeated alignments on a recurring basis, as testing 

configurations were modified. Testing at Schwartz Road provided a fairly easy way to 

align the antennas since the road is basically a straight line. 

The data throughput values recorded during the second phase showed that the system had 

a 10 Mbps limitation. This was attributed to the fact that the AirPair 100 units were 

configuring themselves improperly with the network speed auto-negotiation disabled. 

These units default to 100 Mbps when auto-negotiation is disabled, but the laptop 

defaults to 10 Mbps, thereby constricting data throughput to the lower of the two, 10 

Mbps, with auto-negotiation disabled. This default configuration worked against 

achieving the best possible overall system performance. 

 

The third phase was conducted at the SLF in late August 2005. Pushing the limits of the 

link to this distance over a very uniform path surface confirmed that the expected Fresnel 

Zone degradation exists at a distance of 3.2 miles with the E-R Wi-Fi antennas mounted 

at a low 2-meter height. The best received signal level (RSL) achieved during this test 

had a link performance unacceptable to perform a data throughput measurement test. For 

this reason, no throughput data was collected during this phase, despite the link tool 

theoretically indicating that the link should be capable of closing (passing data.) 

For phase four the unit’s were configured with the network speed auto negotiation 

enabled. The system was returned to Schwarz Road to verify that this setting was 

limiting the data throughput. Initially the units were placed 2.5 miles apart. The system 

performed as expected (data throughput averaging around 70 Mbps). The units were then 

tested at distances of 2.0, 1.5, and 1.0 miles apart, and data rates much closer to the 

theoretical maximum of 100 Mbps were achieved and measured. 

Figure 3-11 shows all the data collected during the second and fourth phases of field 

testing. It shows throughput in Mbps over the distance (in miles) separating the two ends 

of the AirPair 100 system. 

66
ECT – Phase 4 

 

Throughput Vs Distance

0

10

20

30

40

50

60

70

80

90

0.0 1.0 2.0 3

Distance - Mi

Throughput - Mbps

.0

AutoNeg Disabled

AutoNeg Enabled

Figure 3-11 Throughput Versus Distance 

Figure 3-12 shows the calculated average data throughput for the same distances. 

67
ECT – Phase 4 

 

Average Throughput Vs Distance

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

80.0

0.0 0.5 1.0 1.5 2.0 2.5 3.0

Distance - Mi

Throughput - Mbps

AutoNeg Disabled

AutoNeg Enabled

Figure 3-12 Average Throughput versus Distance 

3.9 E-R WI-FI SECURITY CONCERNS 

Security for typical Wi-Fi links is usually achieved using WEP, or newer security 

protocols. As the emphasis this year was on simply achieving communication over longer 

range distances than possible with Wi-Fi, at locations for which physical security through 

zone of control would be adequate, additional protocols for securing E-R Wi-Fi links 

were not investigated. In short, the usual protocols would provide as much security as 

for shorter wide area networks utilizing wireless access points, and no additional security 

was deemed necessary. 

For fielded links, operating where zone of control limiting undesired intruders is not 

possible, more secure protocols will need to be employed. This is recommended for a 

future set of tests, during the initial testing in an operational configuration during field 

testing. This testing is planned for the coming year. 

3.10 E-R WI-FI SUMMARY AND RECOMMENDATIONS 

The precept of ECT during Phases 2 and 3 was to investigate newly-introduced Wi-Fi, 

UWB, and FSO products while they were still in their infancy, and thereby influence the 

68
ECT – Phase 4 

 

development of these developing products as early as possible, before we needed 

operational systems on the Range at KSC. For both Wi-Fi and Extended-Range Wi-Fi, 

we are now much closer to fielding practical systems at KSC, and we have clearly gained 

an in-depth understanding of the operational limits of extended range Wi-Fi technology 

within the unique KSC environment. As in any activity, the state of the art continues to 

improve. And we have found that there are critical unique aspects of the KSC 

environment that force a shift from the priorities that commonly exist for Wi-Fi systems 

intended for urban areas. 

For example, in urban environments, or in densely occupied office environments, where 

many users can be located within a common area within range of a single wireless access 

point, the need for strong security protocols is clearly mandated. 

However, within the Range environment of KSC, over long distance areas for which zone 

of control is clearly adequate to protect operational links, less strong security protocols 

are entirely feasible for the next few years for initial operational testing. Clearly, though, 

stronger protection against intrusion and surreptitious use of E-R Wi-Fi links will be 

required for networking remote sites at KSC with the existing wired infrastructure, and 

this protection must be developed and tested using stronger protection protocols than the 

existing WEP and similar techniques. These topics must be addressed in the next set of 

activities, before transitioning to fielded operational E-R Wi-Fi systems. 

We are clearly much closer to our goal of fielding high data-rate rates over longer 

distances at KSC remote sites with Wireless Ethernet (Wi-Fi) systems.

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ECT – Phase 4 

 

4.0

70
ECT – Phase 4 

 

ULTRA WIDE BAND

4.1 INTRODUCTION 

Emerging Ultra Wideband (UWB) systems hold the promise of delivering wireless data 

at high speeds, exceeding hundreds of megabits per second over typical distances of 10 

meters or less. 

Last year’s ECT-related UWB activities investigated the timing accuracies required for 

achieving low Bit Error Rates despite the presence of timing errors which can otherwise 

adversely affect the positional accuracies and Bit Error Rates of UWB systems. The 

prior year’s ECT-related UWB activity provided an investigation of the methods of 

detecting non-cooperative UWB signals over distances that are essentially as far as the 

actual communication distances usable by UWB receivers utilizing all detailed waveform 

parameters, and resulted in a patent application. 

The emphasis in this year’s activities involves optimizing UWB waveforms for achieving 

overall system power consumption efficiency, and additionally monitoring industry 

progress towards achieving the necessary foundation infrastructure needed to make UWB 

system components practical. 

4.2 BACKGROUND 

In the near future, wireless broadband communications systems will require data rates 

exceeding hundreds of mega bits per second (Mbps). To address these approaching 

demands, emerging Ultra Wideband (UWB) systems offer an ideal physical (PHY) layer 

solution to address wireless personal area networking (WPAN) needs over short ranges. 

As UWB modulation becomes better understood and data rates increase to near their 

maximum potentials, the emphasis will likely switch to maximizing efficiency of UWB 

systems through optimizing UWB waveforms to accommodate transmitting at lower 

transmitter power levels. 

The ECT Phase 4 research this year explored the waveform details required to support 

the operation of UWB OFDM systems in such a future communication landscape. 

Additionally, the activities this year tracked the progress among competing camps 

proposing a unifying UWB alternative standard for implementing an emerging 

communication technology. Unfortunately, the UWB task group (802.15.3a) still 

remains deadlocked, where it has remained since 2003, with two incompatible 

approaches. This is/was the standard that was supposed to enable cable TV without the 

cable and permit interfacing between flat panel HD TVs and HD playback recorders, as 

well as between cable TV inputs into homes and remote wall-mounted flat-panel HD 

TVs, all without the wires and cables required to date. 

71
ECT – Phase 4 

 

4.3 UWB WAVEFORM INVESTIGATION UPDATE 

Instead of using the traditional Pulse Position Modulation (PPM), Pulse Amplitude 

Modulation (PAM), Binary Phase Shift Keying (BPSK), and On/Off Keying (OOK) 

modulations investigated in the first two years of UWB research, and the alternate 

approach investigated last year of OFDM (Orthogonal Frequency Division Multiplexing), 

the emphasis this year is instead to focus on the physical layer (PHY) and investigate 

fundamental techniques for improving the power efficiency of future UWB systems 

through investigating choice of waveform optimization techniques. 

Why does any particular choice of monocycle (UWB) waveform reduce power 

consumption? It is really not that less data is lost, or that the computational power is 

reduced through having a more optimal monocycle waveform. Instead, it is because: 

1. For any given modulation selected, the signal to noise ratio (SNR) is what most 

determines the Bit Error Rate (BER), provided that timing errors are otherwise 

minimized (the effects of which were analyzed last year), interference is 

otherwise minimized, and jamming signals are not present. 

2. Some types of modulation are more robust than others, that is, they provide better 

BER performance at low SNR, when operated in thermal noise-limited 

environment. 

3. A monocycle is very close to being the optimal Gaussian signal that can provide 

the most robust signaling scheme in an AWGN (Average White Gaussian Noise) 

environment, thereby providing the very best BER at low SNR, as noted in the 

activities of two years prior. 

4. Because of the ability of a monocycle to operate at the lowest SNR while 

providing the best communication BER, a communication link designed around 

UWB monocycles is theoretically capable of being the most efficient for a given 

transmitted power in terms of BER performance. Equivalently, for achieving a 

given BER, it becomes possible to use a monocycle waveform to permit using the 

least amount of transmitted power of any other modulation type. (Not just known 

modulation formats, but of all possible modulation formats!) 

5. Relative to where power is most consumed, transmitters generally use the most 

power; hence, for many modulation types, the amount of DSP chip power used 

for demodulation in a receiver is roughly constant, ceteris paribus. It is the 

transmitter power that matters most in terms of power consumption efficiency. 

6. Because of this optimal signaling characteristic, a UWB waveform based on a 

monocycle uses the least amount of transmitted power, and hence provides the 

most power-efficient communication link that is theoretically possible. 

72
ECT – Phase 4 

 

7. This advantage is an even bigger deal when networks made up of large numbers 

of sensors are used. Such a network is most able to benefit from UWB's optimal 

signaling advantage, as there is typically only one receiver, and a very large 

number of transmitters. UWB is inherently more of an advantage over other 

modulation types for optimizing power consumption in such a wireless sensor 

grid. It would also become possible to have battery-powered UWB sensors that 

would permit total freedom from the ac power mains in many applications when 

operation over only a few weeks or less is desired from the UWB wireless sensor 

grid transmitters. The receiver, of course, could be centrally located where ac 

power was available. 

Based on these observations, research activities with Ms. Tammara Massey, NASA 

Harriett Jenkins Fellowship student and UCLA graduate student, were commenced this 

year. Ms. Massey is continuing her research into the next fiscal year, and this research 

will be continued, in a joint effort, among ECT personnel and Ms. Massey. It is 

anticipated that an MSEE thesis will ultimately result from this jointly-conducted 

research work. Ms. Massey, however, is not utilizing any budget from ECT, but is 

instead funded through the NASA Harriett Jenkins Fellowship program. 

4.4 STANDARDS UPDATES 

A major UWB news announcement was released on May 9, 2005, and continues to build; 

UWB and Bluetooth are effectively merging into a new standard. The newly-merged 

standard is to be known as 802.15.4a. 

This merger of standards will provide an upgrade path for Bluetooth, a short range 

WPAN comm technology that is currently locked to a maximum data rate of roughly 3 

Mb/s, and will enable it to achieve data rates of 480 Mb/s and higher through integrating 

a second PHY layer implemented with UWB into the next version of Bluetooth. 

It is not clear if this is a viable approach to achieving higher performance, or if it is 

merely the last faint gasp of two technologies that have seen their fortunes decline 

somewhat over the past 2 years due to the failure of the market to settle on a particular 

UWB standard and due to the rapid growth of Wi-Fi and related similar wireless 

technologies (Wi-Max, etc.) at the expense of Bluetooth -- Bluetooth market share has 

never done well in North America, although it has done better in Europe. In North 

America, its largest use has been capturing the hands-free earpiece comm link for GSM 

cellphones, building on technology first introduced in Europe for their GSM phones. 

Meanwhile, UWB remains a "future technology" due to its lack of a unifying compatible 

standard, among either IEEE committees and FCC recognized regulations.. 

4.5 UWB ANTENNA UPDATES 

Significant advances were made this year among UWB industry participants into 

developing wider bandwidth UWB antennas. Perhaps most significant, Fractus, of 

Barcleona, Spain, announced in early September 2005 the release of a UWB antenna 

73
ECT – Phase 4 

 

design dubbed the UWB Media+ Chip Antenna. This antenna operates over the 3.1-5.0 

GHz sub-banded spectrum specified by the WiMedia Alliance, which includes members 

Intel, Texas Instruments, Microsoft, Philips Electronics, Nokia, and Staccato 

Communications among others. The WiMedia Alliance is one of the two consortia 

competing for dominance among the UWB task group (802.15.3a). Staccato claims to 

have tested the fractal-based antenna and, based on successful tested performance, began 

offering it as an optional antenna for use with its all-CMOS UWB chip. Fractus’ UWB 

antenna measures 10.0 mm x 10.0 mm x 0.8mm, and is claimed to provide an omnidirectional radiation pattern at high efficiency. 18

4.6 SUMMARY OF RESULTS 

The primary UWB-related activity this year was simply monitoring the rather slow 

progress in the vendor community and among standards committees for UWB 

technology, while additionally conducting joint research through the NASA Harriett 

Jenkins Fellowship program with NASA Fellowship student Ms. Tammara Massey. Due 

to the uncertainty of which of the two competing UWB approaches may ultimately win 

the majority of market share, the release of new designs from vendors was noticed to 

have slowed noticeably this year, since the initial flurry of activity two and three years 

ago. 

Nonetheless, UWB remains a most intriguing technology, with communication 

capabilities that largely have been under-appreciated among the general community of 

First Mile/Last Mile communication link planners. 

4.7 RECOMMENDATIONS FOR FUTURE RESEARCH 

Recommendations for continuing UWB research in the new fiscal year include 

investigating, selecting, procuring, and testing new UWB Evaluation Kits released in 

2005, one of which may help crystalize the market into settling on a de-facto industry 

standard. 

Likewise, the research into optimal power-saving UWB waveforms will be continued at 

no or low cost to the project through utilizing the resources of the NASA Harriett Jenkins 

Fellowship student program, through working with UCLA graduate student Ms. 

Tammara Massey. 

This way, UWB technology will be monitored and best tailored for future use on the 

Range. 

 

18 “Fractal antenna pioneer targets UWB”, John Walko, EE Times, 09/13/05, 

http://www.eetimes.com/news/latest/showArticle.jhtml?articleID=170702765 

74
ECT – Phase 4 

 

5.0 ECT SUMMARY RECOMMENDATIONS FOR CONTINUED 

RESEARCH 

The following major task activity areas are recommended for continued research in the 

next fiscal year for emerging communication technology development: 

1. Networked FSO 

2. FSO pre-operational field testing during inclement weather 

3. Extended-Range Wi-Fi pre-operational field testing during inclement 

weather. 

4. UWB Evaluation Kit (EVK) procurement and testing. 

5. Monitor emerging communication technology development. 

Within these five major task activity areas, the following detailed tasks are 

recommended: 

1. Networked FSO: 

• Conduct an industry survey of FSO system hardware suitable for 

implementing a small networked optical FSO system, and procure a fixed, 

non-tracking, wide-beam optical FSO system set of components with 

redundant optical beams to investigate the limits of networking multiple 

FSO systems. 

2. FSO Pre-operation Field Testing: 

• Update previously-generated test procedures, while adapting and 

expanding these procedures to account for the multiple FSO OTUs. 

• Test the FSO system exemplars for Bit Error Rate, and throughput rates 

versus weather-induced degradation conditions (e.g., fog, rain, etc.) when 

operating in a networked configuration. 

• Test the performance limits of FSO hardware within the unique 

environment of KSC, with data path links over both water and over land, 

comparing the applicability of this technology to KSC’s needs versus the 

single FSO link tested previously, including during inclement weather. 

3. Extended-Range Wi-Fi Pre-Operational Field Testing 

• Update previously-generated test procedures, while adapting and 

expanding these procedures to account for the longer distance Wi-Fi links. 

• Test the E-R exemplars for Bit Error Rate, and throughput rates versus 

weather-induced degradation conditions (e.g., fog, rain, etc.). 

• Test the performance limits of E-R Wi-Fi hardware within the unique 

environment of KSC, with data path links situated over both water and 

over land, comparing the applicability of this technology to KSC’s needs 

versus the shorter-range Wi-Fi links tested previously, including during 

inclement weather. 

75
ECT – Phase 4 

 

4. UWB Evaluation Kit Procurement and Testing: 

• Conduct an industry survey of UWB EVK hardware suitable for 

implementing a short range (<10 m) communication system, and procure 

an EVK set of components with a data rate of several hundred Mb/s. 

Update previously-generated test procedures, while adapting and 

expanding these procedures for testing the UWB evaluation kit for 

position aware functionality. 

5. Monitor Emerging Communication Technology Development 

• Review current UWB and FSO products and theoretical developments 

through attending two major communication conferences. 

These task order activities are needed to achieve the 24/7, always-on, highly-mobile 

vision of an interconnected communication for use on the Range employing First Mile / 

Last Mile extensions to the existing Range communication infrastructure. 

76
ECT – Phase 4 

 

APPENDIX A: Acronyms & Definitions 

APD Avalanche Photodetector Diodes 

ARTWG Advanced Range Technologies Working Group 

ASTWG Advanced Spaceport Technologies Working Group 

AWGN Average White Gaussian Noise 

BER Bit Error Rate 

BPSK Binary Phase Shift Keying 

BSD Berkeley Software Distribution from University of California at Berkeley; 

also known as BSD Unix 

BW Bandwidth 

CDR Clock and Data Recovery 

CEV Crew Exploration Vehicle 

COTS Commercial off the shelf 

dB decibel; formally, it is 10 times the logarithm to base 10 of the ratio of 

two powers 

dBe decibel electrical 

dBo decibel optical 

DSP Digital Signal Processing

DW1 DragonWave unit #1 

DW2 DragonWave unit #2 

Eb Energy per bit 

ECT Emerging Communication Technologies 

EDL Engineering Development Laboratories (building) 

E-R WiFi Extended-Range WiFi 

FCC Federal Communications Commission 

FEC Forward Error Correction 

FIRST Future Interagency Range & Spaceport Technologies 

77
ECT – Phase 4 

 

FSO Free Space Optics 

FY Fiscal Year 

GSE Ground Support Equipment 

GSM Global System for Mobile Communication; originally a lengthy French 

acronym shortened to GSM from "Groupe de travail Spéciale pour les 

services Mobiles", but which is now generally considered Anglicised 

HAAT Height above average terrain 

Hz Hertz (cycle per second) 

IFFT Inverse Fast Fourier Transform 

IM/DD Intensity Modulated / Direct Detection 

IP Internet Protocol; used with Transmission Control Protocol (TCP), 

TCP/IP forms the rule set that enables computers to communicate via the 

Internet 

MBOA Multi-Band OFDM (Orthogonal Frequency Division Multiplexed) 

Alliance; one of the two competing UWB industry partnerships 

Mbps Megabits per second; bits per second 6 10

Mux Multiplexer 

NASA National Aeronautics and Space Administration 

Neff Effective noise 

OE Optical to Electrical 

OFDM Orthogonal Frequency Division Multiplexing 

OOK ON/OFF Keying 

OTU Optical Transfer Unit 

PAM Pulse Amplitude Modulation 

PAT Performance Analysis Tool 

PDF Probability Density Function 

PHY Physical Layer 

PIN Positive-Intrinsic-Negative (diodes) 

PPM Pulse Position Modulation 

78
ECT – Phase 4 

 

PRBS Pseudo-Random Bit Sequence 

R&D Research & Development 

RF Radio Frequency 

RISM Range Information Systems Management 

Rx Receiver 

SBRDS Space Based Range Distributed Subsystem 

SLF Shuttle Landing Facility 

SNR Signal to Noise Ratio 

<SNR> Time average value of Signal to Noise Ratio 

SPIE Society of Photo-Optical Instrumentation Engineers, also known as “SPIE 

– The International Society for Optical Engineering” 

TCP Transmission Control Protocol; used with Internet Protocol (IP), TCP/IP 

forms the rule set that enables computers to communicate via the Internet 

Tx Transmitter 

UI Unit Interval 

UK United Kingdom 

Unk Unknown 

UWB Ultra Wide Band 

WiFi Wireless Fidelty 

WSTTCP Windows Socket port of Test Transmission Control Protocol software 

ported originally from BSD operating system TTCP utility by Sungjin 

Chun <sjchun@janus.sst.co.kr> to Windows Sockets as WSTTCP in 1996 

WPAN Wireless Personal Area Network 

Wx Weather 

<SNR> Time average value of the Signal to Noise Ratio 

 

79
ECT – Phase 4 

 

80
ECT – Phase 4 

 

APPENDIX B: Optical BER Equations For OOK 

The difference in dBe (electrical decibels) versus dBo (optical decibels) primarily comes 

from the optical to electrical conversions occurring in photodiodes. A similar difference 

also occurs when deriving theoretical BER equations for RF vs. Electro-Optical OOK 

systems in terms of signal-to-noise ratios. 

To see this difference, let the output current from the receiver photodiode be (neglecting 

atmospheric effects): 

s n ii i = + (11) 

where is = signal current and in = noise current. Hence, s < i i >= and . If 

we assume the noise to be zero-mean Gaussian, then: 

22 2

inn σ σ= =< i >

2

2

1 ( ) exp 2 2 n

n n

i p i

σ π σ

⎛ ⎞ = −⎜

⎝ ⎠⎟ (12) 

2

2

1 ( ) ( ) exp . 2 2

s s n

n n

i i p i

σ π σ +

⎛ ⎞ − = −⎜

⎝ ⎠⎟ (13) 

The first expression is the pdf on noise alone and the second is the pdf for signal and 

noise. Hence, the false alarm probability and detection probability are given by: 

1 ( ) 2 2 fa n T

n

T P p i di erfc

σ

∞

∫

⎛ ⎞ = = ⎜

⎜

⎝ ⎠

⎟

⎟ (14) 

det

1 ( ) 2 2

s T s n

n

T i P p i di erfc

σ

∞

∫ +

⎛ ⎞ − = = ⎜

⎜

⎝ ⎠

⎟

⎟ (15) 

where T is the threshold. The error probability (BER) for a digital system is defined by: 

1 1

2 2

BER P P = + fa fade (16) 

where For OOK, set a threshold halfway between “ON” and “OFF”, i.e., 

at 

det 1 Pfade = − P .

0.5 T = si . In this case, we find: 

1

2 2 2

s fa fade

n

i P P erfc

σ

⎛ ⎞ = = ⎜

⎜

⎝ ⎠

⎟

⎟ (17) 

81
ECT – Phase 4 

 

2

2

1 11 , 2 22 2 2 2

s s

n n

i i z BER erfc erfc z SNR

σ σ

⎛ ⎞ ⎛ ⎞ == = ⎜ ⎟ ⎜ ⎟ ⎝ ⎠ ⎝ ⎠

= (18) 

The effect of the optical power to electrical current conversion using a photodiode is to 

add approximately 6 dB to the theoretical OOK <SNR> required for electro-optical 

versus RF/electrical communication systems, to achieve the same BER performance.

82
ECT – Phase 4 

 

APPENDIX C: Extended Range Wi-Fi Test Results 

The following data were collected during the second stage of testing. The testing was 

performed at Schwartz Road at distances ranging from 1.0 to 2.5 miles. During all of 

these tests, the system's network interface auto-negotiation was disabled. DW1 

represents the East AirPair 100 unit that was connected to the laptop transmitting the test 

data. DW2 represents the West unit receiving the test data. 

 DW1 DW2 

Run Date Dist Bytes Auto Tx RSL Eb/No Thrpt Tx RSL Eb/No Thrpt 

 Mi Neg dB dBm dB Mbps dB dBm dB Mbps 

1 7/5/05 1.0 81920000 Disabled 3 -51.5 n/a 6.1 3 -47.7 n/a 6.1 

2 7/5/05 1.0 81920000 Disabled 3 -51.5 n/a 6.5 3 -47.7 n/a 6.5 

3 7/5/05 1.0 81920000 Disabled 3 -51.5 n/a 5.5 3 -47.7 n/a 5.5 

4 7/5/05 1.0 81920000 Disabled 3 -51.5 n/a 5.5 3 -47.7 n/a 5.6 

5 7/5/05 1.0 16777216 Disabled 3 -51.5 n/a 5.0 3 -47.7 n/a 5.0 

6 7/5/05 1.0 16777216 Disabled 3 -51.5 n/a 6.3 3 -47.7 n/a 6.3 

7 7/5/05 1.0 16777216 Disabled 3 -51.5 n/a 7.3 3 -47.7 n/a 7.3 

8 7/5/05 1.5 16777216 Disabled 3 -59.3 n/a 5.2 3 -56.0 n/a 5.2 

9 7/5/05 1.5 16777216 Disabled 3 -59.3 n/a 6.1 3 -56.0 n/a 6.1 

10 7/5/05 1.5 16777216 Disabled 3 -59.3 n/a 6.3 3 -56.0 n/a 6.3 

11 7/5/05 1.5 81920000 Disabled 3 -59.3 n/a 6.1 3 -56.0 n/a 6.1 

12 7/5/05 1.5 81920000 Disabled 3 -59.3 n/a 6.4 3 -56.0 n/a 6.4 

13 7/5/05 1.5 81920000 Disabled 3 -59.3 n/a 5.8 3 -56.0 n/a 5.8 

14 7/6/05 2.5 81920000 Disabled 3 -62.9 n/a 6.8 3 -59.9 n/a 6.7 

15 7/6/05 2.5 81920000 Disabled 3 -62.9 n/a 6.6 3 -59.9 n/a 6.6 

16 7/6/05 2.5 81920000 Disabled 3 -62.9 n/a 7.2 3 -59.9 n/a 7.2 

17 7/6/05 2.5 16777216 Disabled 3 -62.9 n/a 6.5 3 -59.9 n/a 6.4 

18 7/6/05 2.5 16777216 Disabled 3 -62.9 n/a 7.4 3 -59.9 n/a 7.4 

19 7/6/05 2.5 16777216 Disabled 3 -62.9 n/a 7.9 3 -59.9 n/a 7.7 

20 7/6/05 2.0 81920000 Disabled 3 -63.9 n/a 6.8 3 -59.6 n/a 6.8 

21 7/6/05 2.0 81920000 Disabled 3 -63.9 n/a 6.6 3 -59.6 n/a 6.6 

22 7/6/05 2.0 81920000 Disabled 3 -63.9 n/a 6.5 3 -59.6 n/a 6.5 

23 7/6/05 2.0 16777216 Disabled 3 -63.9 n/a 6.3 3 -59.6 n/a 6.2 

24 7/6/05 2.0 16777216 Disabled 3 -63.9 n/a 6.4 3 -59.6 n/a 6.4 

25 7/6/05 2.0 16777216 Disabled 3 -63.9 n/a 8.2 3 -59.6 n/a 8.0 

26 8/9/05 2.0 16777216 Disabled 3 -61.1 n/a 8.5 3 -58.4 n/a 8.4 

27 8/9/05 2.0 16777216 Disabled 3 -61.1 n/a 6.8 3 -58.4 n/a 6.8 

28 8/9/05 2.0 16777216 Disabled 3 -61.1 n/a 8.0 3 -58.4 n/a 7.8 

29 8/9/05 2.0 81920000 Disabled 3 -61.1 n/a 7.4 3 -58.4 n/a 7.4 

30 8/9/05 2.0 81920000 Disabled 3 -61.1 n/a 7.4 3 -58.4 n/a 7.4 

31 8/9/05 2.0 81920000 Disabled 3 -61.1 n/a 8.7 3 -58.4 n/a 8.7 

32 8/10/05 1.0 16777216 Disabled 3 -52.8 n/a 8.0 3 -48.5 n/a 7.9 

33 8/10/05 1.0 16777216 Disabled 3 -52.8 n/a 8.0 3 -48.5 n/a 8.0 

34 8/10/05 1.0 16777216 Disabled 3 -52.8 n/a 6.4 3 -48.5 n/a 6.4 

83
ECT – Phase 4 

 

35 8/10/05 1.0 16777216 Disabled 3 -52.8 n/a 7.5 3 -48.5 n/a 7.4 

36 8/10/05 1.0 16777216 Disabled 3 -52.8 n/a 7.6 3 -48.5 n/a 7.6 

37 8/10/05 1.0 81920000 Disabled 3 -52.8 n/a 7.4 3 -48.5 n/a 7.4 

38 8/10/05 1.0 81920000 Disabled 3 -52.8 n/a 6.9 3 -48.5 n/a 6.9 

39 8/10/05 1.0 81920000 Disabled 3 -52.8 n/a 6.7 3 -48.5 n/a 6.7 

40 8/10/05 1.0 81920000 Disabled 3 -52.8 n/a 6.4 3 -48.5 n/a 6.4 

41 8/10/05 1.0 81920000 Disabled 3 -52.8 n/a 7.3 3 -48.5 n/a 7.3 

42 8/10/05 1.0 81920000 Disabled 3 -52.8 n/a 6.7 3 -48.5 n/a 6.6 

43 8/10/05 1.0 81920000 Disabled 3 -52.8 n/a 6.8 3 -48.5 n/a 6.8 

44 8/10/05 2.5 16777216 Disabled 3 -63.8 n/a 7.5 3 -58.9 n/a 7.4 

45 8/10/05 2.5 16777216 Disabled 3 -63.8 n/a 7.6 3 -58.9 n/a 7.6 

46 8/10/05 2.5 16777216 Disabled 3 -63.8 n/a 6.8 3 -58.9 n/a 6.8 

47 8/10/05 2.5 81920000 Disabled 3 -63.8 n/a 7.3 3 -58.9 n/a 7.3 

48 8/10/05 2.5 81920000 Disabled 3 -63.8 n/a 6.8 3 -58.9 n/a 6.8 

49 8/10/05 2.5 81920000 Disabled 3 -63.8 n/a 7.3 3 -58.9 n/a 7.3 

50 8/10/05 2.5 81920000 Disabled 3 -63.8 n/a 7.3 3 -58.9 n/a 7.3 

This next table shows the data collected during the fourth stage of testing. The testing 

was performed at Schwartz Road. The distances range between 1.0 and 2.5 miles of 

separation. During all of these tests the system's network interface auto-negotiation was 

enabled. DW1 represents the AirPair 100 unit that was connected to the laptop 

transmitting the test data. DW2 represents the unit receiving the test data. 

84
ECT – Phase 4 

 

 DW1 DW2 

Run Date Dist Bytes Auto Tx RSL Eb/No Thrp Tx RSL Eb/No Thrpt 

 Mi Neg dB dBm dB Mbps dB dBm dB Mbps 

95 9/13/05 2.5 16777216 Enabled 3 -62.2 17.1 73.6 3 -56.9 22.3 72.8 

96 9/13/05 2.5 16777216 Enabled 3 -62.2 17.1 74.9 3 -56.9 22.3 74.9 

97 9/13/05 2.5 16777216 Enabled 3 -62.2 17.1 63.8 3 -56.9 22.3 63.5 

98 9/13/05 2.5 16777216 Enabled 3 -62.2 17.1 69.8 3 -56.9 22.3 69.8 

99 9/13/05 2.5 16777216 Enabled 3 -62.2 17.1 69.8 3 -56.9 22.3 70.2 

100 9/13/05 2.5 81920000 Enabled 3 -62.2 17.1 68.5 3 -56.9 22.3 68.5 

101 9/13/05 2.5 81920000 Enabled 3 -62.2 17.1 70.7 3 -56.9 22.3 70.6 

102 9/13/05 2.5 81920000 Enabled 3 -62.2 17.1 70.5 3 -56.9 22.3 70.4 

103 9/13/05 2.5 81920000 Enabled 3 -62.2 17.1 70.0 3 -56.9 22.3 70.1 

104 9/13/05 2.5 81920000 Enabled 3 -62.2 17.1 70.4 3 -56.9 22.3 70.4 

105 9/13/05 2.0 16777216 Enabled 3 -58.3 19.3 72.5 3 -53.3 22.9 72.5 

106 9/13/05 2.0 16777216 Enabled 3 -58.3 19.3 69.1 3 -53.3 22.9 69.1 

107 9/13/05 2.0 16777216 Enabled 3 -58.3 19.3 69.4 3 -53.3 22.9 69.1 

108 9/13/05 2.0 16777216 Enabled 3 -58.3 19.3 70.2 3 -53.3 22.9 70.2 

109 9/13/05 2.0 16777216 Enabled 3 -58.3 19.3 70.5 3 -53.3 22.9 70.5 

110 9/13/05 2.0 81920000 Enabled 3 -58.3 19.3 69.3 3 -53.3 22.9 69.3 

111 9/13/05 2.0 81920000 Enabled 3 -58.3 19.3 72.6 3 -53.3 22.9 72.6 

112 9/13/05 2.0 81920000 Enabled 3 -58.3 19.3 72.6 3 -53.3 22.9 72.6 

113 9/13/05 2.0 81920000 Enabled 3 -58.3 19.3 72.5 3 -53.3 22.9 72.6 

114 9/13/05 2.0 81920000 Enabled 3 -58.3 19.3 72.2 3 -53.3 22.9 72.2 

115 9/13/05 1.5 16777216 Enabled 3 -56.3 19.8 71.7 3 -49.4 23.7 72.1 

116 9/13/05 1.5 16777216 Enabled 3 -56.3 19.8 71.3 3 -49.4 23.7 71.7 

117 9/13/05 1.5 16777216 Enabled 3 -56.3 19.8 76.2 3 -49.4 23.7 76.1 

118 9/13/05 1.5 16777216 Enabled 3 -56.3 19.8 64.1 3 -49.4 23.7 64.4 

119 9/13/05 1.5 16777216 Enabled 3 -56.3 19.8 75.7 3 -49.4 23.7 76.6 

120 9/13/05 1.5 81920000 Enabled 3 -56.3 19.8 71.4 3 -49.4 23.7 71.4 

121 9/13/05 1.5 81920000 Enabled 3 -56.3 19.8 72.0 3 -49.4 23.7 72.0 

122 9/13/05 1.5 81920000 Enabled 3 -56.3 19.8 75.9 3 -49.4 23.7 75.8 

123 9/13/05 1.5 81920000 Enabled 3 -56.3 19.8 67.7 3 -49.4 23.7 67.7 

124 9/13/05 1.5 81920000 Enabled 3 -56.3 19.8 73.2 3 -49.4 23.7 73.2 

125 9/14/05 1.0 16777216 Enabled 3 -49.9 21.1 64.4 3 -43.4 21.3 74.0 

126 9/14/05 1.0 16777216 Enabled 3 -49.9 21.1 77.4 3 -43.4 21.3 77.5 

127 9/14/05 1.0 16777216 Enabled 3 -49.9 21.1 70.9 3 -43.4 21.3 70.9 

128 9/14/05 1.0 16777216 Enabled 3 -49.9 21.1 74.4 3 -43.4 21.3 74.4 

129 9/14/05 1.0 16777216 Enabled 3 -49.9 21.1 75.7 3 -43.4 21.3 75.7 

130 9/14/05 1.0 81920000 Enabled 3 -49.9 21.1 74.1 3 -43.4 21.3 74.1 

131 9/14/05 1.0 81920000 Enabled 3 -49.9 21.1 72.6 3 -43.4 21.3 72.6 

132 9/14/05 1.0 81920000 Enabled 3 -49.9 21.1 71.0 3 -43.4 21.3 71.0 

133 9/14/05 1.0 81920000 Enabled 3 -49.9 21.1 77.2 3 -43.4 21.3 77.2 

134 9/14/05 1.0 81920000 Enabled 3 -49.9 21.1 73.8 3 -43.4 21.3 73.8 

85
ECT – Phase 4 

 

86
RISM Phase 1 

REPORT DOCUMENTATION PAGE Form Approved 

OMB No. 0704-0188

Public reporting burden for this collection of information is estimated to average I hour per response, including the time for reviewing instructions, searching existing 

data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate 

or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for 

Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302, and to the Office of Management and Budget, Paperwork 

Reduction Project (0704-0188), Washington, DC 20503. 

1. AGENCY USE ONLY (Leave blank) 

 

2. REPORT DATE 

September 2005 

3. REPORT TYPE AND DATES COVERED 

Technical Memorandum – 2004-2005 

4. TITLE AND SUBTITLE 

Emerging Communication Technologies (ECT) Phase 4 Report 

6. AUTHOR(S) 

Gary L. Bastin, William G. Harris, José A. Marín, 

Richard A. Nelson 

5. FUNDING NUMBERS 

 

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 

ASRC, ASRC-10, John F. Kennedy Space Center, FL 32815 

NASA, YA-D7, John F. Kennedy Space Center, FL 32899 

8. PERFORMING ORGANIZATION 

REPORT NUMBER 

NASA TM-2005-212565 

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 

 

10. SPONSORING/MONITORING 

AGENCY REPORT NUMBER 

NASA TM-2005-212565 

11. SUPPLEMENTARY NOTES 

 

12a. DISTRIBUTION/AVAILABILITY STATEMENT 

Unclassified – Unlimited Distribution: 

Standard 

Subject Category: 

Availability: NASA CASI (301) 621-0390 

12b. DISTRIBUTION CODE 

 

13. ABSTRACT (Maximum 200 words) 

The Emerging Communication Technology (ECT) project investigated three First Mile communication 

technologies in support of NASA’s Crew Exploration Vehicle (CEV), Advanced Range Technology 

Working Group (ARTWG), and the Advanced Spaceport Technology Working Group (ASTWG). These 

First Mile technologies have the purpose of interconnecting mobile users with existing Range 

Communication infrastructures on a 24/7 basis. 

ECT is a continuation of the Range Information System Management (RISM) task started in 2002. This 

is the fourth year of the project. 

15. NUMBER OF PAGES 

96 

14. SUBJECT TERMS 

Range Information Systems, Emerging Communication Technologies, 

Advanced Communication, FSO, UWB, Wi-Fi, Wireless, Ethernet, 

Lasercom, Ranges, Spaceports 

16. PRICE CODE 

 

17. SECURITY 

CLASSIFICATION OF 

REPORT 

Unclassified 

18. SECURITY 

CLASSIFICATION OF 

THIS PAGE 

Unclassified 

19. SECURITY 

CLASSIFICATION OF 

ABSTRACT 

Unclassified 

20. LIMITATION 

OF ABSTRACT 

 

NSN 7540-01-280-5500 Standard Form 298 (Rev. 2-89) 

Prescribed by ANSI Std. Z-39-18 298-102

 
ECT – Phase 4