Tricia Gilbert, Jenny Jin, Jason Berger, and Steve Henriksen

ITT Corporation, Herndon, Virginia 

Additional Technologies and Investigations for 

Provision of Future Aeronautical Communications

NASA/CR—2008-214987

February 2008

WP13
NASA STI Program . . . in Profi le

Since its founding, NASA has been dedicated to the 

advancement of aeronautics and space science. The 

NASA Scientifi c and Technical Information (STI) 

program plays a key part in helping NASA maintain 

this important role.

The NASA STI Program operates under the auspices 

of the Agency Chief Information Offi cer. It collects, 

organizes, provides for archiving, and disseminates 

NASA’s STI. The NASA STI program provides access 

to the NASA Aeronautics and Space Database and 

its public interface, the NASA Technical Reports 

Server, thus providing one of the largest collections 

of aeronautical and space science STI in the world. 

Results are published in both non-NASA channels 

and by NASA in the NASA STI Report Series, which 

includes the following report types:

• TECHNICAL PUBLICATION. Reports of 

completed research or a major signifi cant phase 

of research that present the results of NASA 

programs and include extensive data or theoretical 

analysis. Includes compilations of signifi cant 

scientifi c and technical data and information 

deemed to be of continuing reference value. 

NASA counterpart of peer-reviewed formal 

professional papers but has less stringent 

limitations on manuscript length and extent of 

graphic presentations.

• TECHNICAL MEMORANDUM. Scientifi c 

and technical fi ndings 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. Scientifi c and 

technical fi ndings by NASA-sponsored 

contractors and grantees.

• CONFERENCE PUBLICATION. Collected 

papers from scientifi c and technical 

conferences, symposia, seminars, or other 

meetings sponsored or cosponsored by NASA.

• SPECIAL PUBLICATION. Scientifi c, 

technical, or historical information from 

NASA programs, projects, and missions, often 

concerned with subjects having substantial 

public interest.

• TECHNICAL TRANSLATION. Englishlanguage translations of foreign scientifi c and 

technical material pertinent to NASA’s mission.

Specialized services also include creating custom 

thesauri, building customized databases, organizing 

and publishing research results.

For more information about the NASA STI 

program, 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 Center for AeroSpace Information (CASI)

 7115 Standard Drive

 Hanover, MD 21076–1320
Tricia Gilbert, Jenny Jin, Jason Berger, and Steve Henriksen

ITT Corporation, Herndon, Virginia 

Additional Technologies and Investigations for 

Provision of Future Aeronautical Communications

NASA/CR—2008-214987

February 2008

WP13

National Aeronautics and

Space Administration

Glenn Research Center

Cleveland, Ohio 44135

Prepared under Contract NNC05CA85C

Prepared for the

Aeronautics Communications Panel (ACP), Working Group T–1

sponsored by the International Civil Aviation Organization (ICAO)

Montreal, Canada, September 19–21, 2007
Available from

NASA Center for Aerospace Information

7115 Standard Drive

Hanover, MD 21076–1320

National Technical Information Service

5285 Port Royal Road

Springfi eld, VA 22161

Available electronically at http://gltrs.grc.nasa.gov

Trade names and trademarks are used in this report for identifi cation 

only. Their usage does not constitute an offi cial endorsement, 

either expressed or implied, by the National Aeronautics and 

Space Administration.

This work was sponsored by the Fundamental Aeronautics Program 

at the NASA Glenn Research Center.

Level of Review: This material has been technically reviewed by NASA expert reviewer.

This report contains preliminary fi ndings, 

subject to revision as analysis proceeds.
NASA/CR—2008-214987 iii

Preface 

The following NASA Contractor Report documents the indepth studies on select technologies that 

could support long-term aeronautical mobile communications operating concepts. This work was 

performed during the third and final phase of NASA’s Technology Assessment for the FAA/ 

EUROCONTROL Future Communications Study (FCS) under a multiyear NASA contract. It includes 

the associated findings of ITT Corporation and NASA Glenn Research Center to the Federal Aviation 

Administration (FAA) as of the end of May 2007. The activities documented in this report focus on three 

final technology candidates identified by the United States, and were completed before sufficient 

information about two additional technology candidates proposed by EUROCONTROL was made 

available. A separate report to be published by NASA (NASA/CR—2008-215144), entitled “Final 

Report on Technology Investigations for Provision of Future Aeronautical Communications” will include 

an assessment of all five final candidate technologies considered by the U.S. agencies (FAA and NASA) 

and EUROCONTROL. It will also provide an overview of the entire technology assessment process, 

including final recommendations. All three phases of this work were performed in compliance with the 

Terms of Reference for the Action Plan number 17 (AP–17) cooperative research agreement among 

EUROCONTROL, FAA, and NASA along with the general guidance of the FAA and EUROCONTROL 

available throughout this study. 

NASA/CR—2008-214987 v

Executive Summary 

E.S.1 Background and Introduction 

The Future Communication Study (FCS) is a cooperative research and development program of the 

Federal Aviation Administration (FAA), National Aeronautics and Space Administration (NASA), and 

EUROCONTROL. This study has several technical themes supporting the definition of a future globally 

interoperable communications system to support air traffic management (ATM) operations in the 

timeframe of 2020 and beyond. One of these themes calls for “investigation of potential communications 

technologies operating inside the very high frequency (VHF) band and outside the VHF band to support 

the long-term mobile communication operation concept considering terrestrial and satellite base 

infrastructure.” The Future Communication Study has been organized and carried out in three phases: 

Technology Prescreening (Phase I), Technology Screening and Indepth Studies (Phase II), and Additional 

Technologies and Investigations for Provision of Future Aeronautical Communications (Phase III). 

As decision-making in the aeronautical environment can be complex, a structured methodology that 

accommodates stakeholder inputs has been defined and applied in the FCS. This approach is shown in 

figure 1. The first set of activities (steps 1A and 1B) included derivation of evaluation criteria and 

metrics. Step 2 is to identify most promising technology candidates. The remaining steps (steps 3 through 

6) contribute to detailed assessment of the most promising candidate technologies. Indepth analysis of the 

considered technologies supported these steps. The process concludes with consideration of the relative 

importance of criteria to identify the best performing technology. 
NASA/CR—2008-214987 vi

This report documents the indepth technology analysis activities and results that were conducted 

during the third phase of the technology investigation (Phase III). The FCS final report will document 

final technology evaluation results and recommendations. 

E.S.2 Phase III Indepth Studies 

 Three indepth studies were conducted as part of the FCS Phase III study efforts to support the 

technology evaluation process and to better understand the applicability of the most promising 

technologies to the future aeronautical communication environment; they are the L-band interference 

testing, the wideband code division multiple access (WCDMA) functional assessment, and the 

P34/TIA(Telecommunications Industry Association)–902 intellectual property assessment. 

E.S.2.1 The L-band Interference Testing 

The focus of the L-band interference testing was to gain an understanding of the L-band interference 

environment and to measure interference for three candidate technologies against the distance measure 

equipment (DME), a navigation system currently operating in the aeronautical L-band spectrum. Before 

any new communication systems can be allowed to share spectrum with DME, a compatibility analysis 

must assess potential degradation of DME system performance. A compatibility analysis of candidate 

technologies with DME in L-band involves many potential interference scenarios, including cosite 

(onboard the aircraft), air-to-air, air-to-ground/ground-to-air, and ground-to-ground. 

For the interference measurements of this study, the cosite interference scenario was emulated. The 

cosite interference scenario serves as a guide for specifying the bounds of interference power used when 

taking measurements. The signal levels used for interference measurements should encompass the power 

ranges that will be seen in practice, and these levels are greatest in the cosite scenario. This is not to say 

that ground stations do not also transmit high power signals, but ground stations are generally separated 

by large distances to mitigate the effects of interference. Antennae onboard the aircraft do not have this 

liberty. Figure 2 illustrates the cosite scenario. 
NASA/CR—2008-214987 vii

Results of the study improved understanding of the interference environment associated with DME. 

While limitations in the test equipment do not provide enough information to address specific 

channelization techniques for future radio system (FRS) candidates, the interference measurements do 

suggest that the addition of an FRS in the DME band may be feasible. Three major findings of the 

interference measurements study are as follows: 

• The power levels expected from continuously transmitting FRS equipment onboard the aircraft 

may be sufficiently high as to cause desensitization in the DME interrogator. This phenomenon 

was evident for all of the FRS candidates, even at large frequency separations for the DME that 

was tested. This finding is not favorable for FRS candidate technologies whose concept of use 

assumes continuous transmissions (e.g., WCDMA). 

• The data also indicate that the DME interrogator is more tolerant to gated transmissions (i.e., 

there is potential for implementation of a technology with a gated waveform; but off-set channels 

may still be required (to be investigated)). A majority of the measurements used 100 percent duty 

cycles, which results in a conservative analysis. Lesser duty cycles may be expected in practice. It 

is expected that low-to-moderate duty cycles will interfere less with DME compared to FRSs with 

high duty cycles. This finding may be favorable for FRS candidate technologies whose concept of 

use assumes noncontinuous transmissions (i.e., L-band digital link (LDL) and P34/TIA–902 

(partial)). 

• Further analysis should be conducted to characterize the relationship between FRS duty-cycle and 

interference susceptibility (the duty-cycle investigation should include more variables than just 

overall duty cycle; there may be some combination of specific timescales of on/off pulses and 

overall duty cycle that results in a seemingly “invisible” waveform from the DME interrogator’s 

perspective.) In the context of this investigation, identification of collocation constraints can also 

be investigated. It is also recommended that different models of DME interrogators be tested to 

provide a range of performance. 

The interference measurements, in conjunction with the concept of use defined for each candidate 

FRS technology, will be used to support the detailed technology evaluations to be documented in the FCS 

final report. 

E.S.2.2 The WCDMA Functional Assessment 

A second indepth analysis was the WCDMA Functional Assessment. The study’s objective was to 

define how the technology could support Communications Operating Concept and Requirements (COCR) 

services. Specifically, the analysis was used to determine the necessary elements of the architecture and 

protocol stack to provision COCR services, which further supported the assessment of cost, certification, 

and standardization of WCDMA in aeronautical applications. A representative result of this analysis, 

mapping of one part of a COCR service, data link initiation capability (DLIC), to WCDMA, is illustrated 

in figure 3. 

Applying the WCDMA standards as defined, this study found that a full complement of WCDMA 

functional elements is required to provision COCR services. Not only the air interface and elements of the 

radio network controller are needed, but also elements of the core network such as home location register 

(HLR), serving general packet radio service (GPRS), support node (SGSN), and gateway GPRS support 

node (GGSN). 
NASA/CR—2008-214987 viii

E.S.2.3 The P34/TIA–902 Intellectual Property Assessment 

The final indepth analysis conducted during Phase III of the FCS technology investigation was the 

P34/TIA–902 intellectual property assessment. This study evaluated the potential impact of the P34/TIA–

902 standard intellectual property in the context of an FRS implementation. Thorough review of the 

patents and consultation with a patent counsel helped develop the following conclusions: 

• The concept of use defined for P34/TIA–902 makes some patents not applicable (e.g., isotropic 

orthogonal transform algorithm (IOTA) physical layer not used in the FCS application and 

associated patents do not apply); also, recommended tailoring of physical layer standard for the 

FCS application results in bypassing of most physical layer patents. 

• Only one patent is assessed as desirable to implement. It is a methodology proposed for power 

amplifier linearization, modification of which would influence the definition of MAC framing 

structure. 

• Most, if not all, patents will expire before timeframe of FCS. 

• These patents are not applicable to companies outside the United States. 

• Intellectual property associated with P34/TIA–902 standard is deemed to have little or no impact 

on the FRS if it is an implementation based on this standard. 
NASA/CR—2008-214987 ix

Contents 

Preface .........................................................................................................................................................iii

Executive Summary ...................................................................................................................................... v

1.0 Background and Introduction.................................................................................................................. 1

1.1 Global Aeronautical Communication Objectives.......................................................................... 1

1.2 Future Communication Study Technology Investigations............................................................ 2

1.3 Stakeholder Inputs......................................................................................................................... 2

1.4 Approach Introduction and Overview........................................................................................... 3

1.5 Supporting Assessments................................................................................................................ 4

2.0 L-Band Interference Measurements........................................................................................................ 5

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

2.1.1 Motivation........................................................................................................................ 5

2.1.2 Objective .......................................................................................................................... 6

2.1.3 Approach .......................................................................................................................... 6

2.1.4 DME System Overview ................................................................................................... 6

2.2 Methodology ................................................................................................................................. 7

2.2.1 Test Setup and Equipment................................................................................................ 7

2.2.2 Test Cases......................................................................................................................... 9

2.2.3 Waveform Development ................................................................................................ 10

2.3 Measurement Results .................................................................................................................. 15

2.3.1 WCDMA/DME Interference Measurements.................................................................. 15

2.3.2 LDL/DME Interference Measurements.......................................................................... 16

2.3.3 P34/DME Interference Measurements ........................................................................... 18

2.4 Conclusions and Future Work..................................................................................................... 22

3.0 WCDMA Functional Assessment......................................................................................................... 23

3.1 Objective ..................................................................................................................................... 23

3.2 Approach ..................................................................................................................................... 23

3.3 WCDMA Network Architecture ................................................................................................. 24

3.4 Selection of Air Traffic Data Link Services................................................................................ 25

3.4.1 Sources of Service Information...................................................................................... 25

3.4.2 Mapping Services Into WCDMA Network Functions ................................................... 27

3.4.3 Logical Mapping ............................................................................................................ 27

3.5 Service Mapping ......................................................................................................................... 27

3.5.1 Logical Mapping ............................................................................................................ 27

3.6 Service Mapping ......................................................................................................................... 28

3.6.1 DLIC Service ................................................................................................................. 28

3.6.2 DLIC to WCDMA Services ........................................................................................... 29

3.6.3 Other Selected Data Link Services................................................................................. 31

3.7 Conclusions ................................................................................................................................. 32

4.0 P34/TIA–902 Intellectual Property Assessment ................................................................................... 33

4.1 Introduction to Intellectual Property ........................................................................................... 33

4.2 Introduction to P34/TIA–902 Standards ..................................................................................... 33

4.2.1 Patents in P34/TIA–902 Standards................................................................................. 34

4.3 Assessment Approach ................................................................................................................. 35

4.3.1 Propose a Recommendation ........................................................................................... 36

4.3.2 Terms and Assumptions................................................................................................. 36

4.4 Patent Assessments ..................................................................................................................... 37

4.4.1 Patent 1........................................................................................................................... 37

4.4.2 Patent 2........................................................................................................................... 37
NASA/CR—2008-214987 x

4.4.3 Patent 3........................................................................................................................... 38

4.4.4 Patent 4........................................................................................................................... 38

4.4.5 Patent 5........................................................................................................................... 39

4.4.6 Patent 6........................................................................................................................... 39

4.4.7 Patent 7........................................................................................................................... 40

4.4.8 Patent 8........................................................................................................................... 40

4.5 Conclusions ................................................................................................................................. 40

5.0 Summary of Results.............................................................................................................................. 42

Appendix A— Unfiltered Interference Measurement Results.................................................................... 45

Appendix B— Additional WCDMA Functional Analysis Results............................................................. 49

Appendix C— Summary of Previous Indepth Assessments....................................................................... 61

Appendix D— List of Acronyms and Abbreviations ................................................................................. 77

References................................................................................................................................................... 80
NASA/CR—2008-214987 1

1.0 Background and Introduction 

1.1 Global Aeronautical Communication Objectives 

The origin of current aeronautical communication objectives can be traced to results of the 

International Civil Aviation Organization (ICAO) Aeronautical Mobile Communication Panel (AMCP) 

from the year 2000 and the Eleventh Air Navigation Conference (ANConf/11), held in Montréal, Canada, 

from September 22 through October 3, 2003. One result of the seventh meeting of the AMCP (AMCP/7) 

in March 2000 was the establishment of a task (Task communication, surveillance, navigation (CNS)–

9102) to carry out the fact-finding and conduct the necessary studies for the development of data links for 

air traffic services and aeronautical operational control. In October 2000, the AMCP working group C 

(WG–C), addressing future air/ground communications, held their first meeting, which included the 

establishment of Action WGC/1–9 to develop a report to recommend a scenario in which a common 

global interoperable communication infrastructure could be ensured for the future. Finally, one of the 

highlights of the formal ICAO Air Navigation Conference was the official report of the Technical and 

Operational Matters in Air Traffic Control Committee (Committee B). This report noted the current state 

of aviation communications and made several recommendations to advance this state. The observations 

included 

• The aeronautical mobile communication infrastructure has to evolve in order to accommodate 

new functions. 

• This evolution would likely require the definition and implementation of new terrestrial and/or 

satellite systems that operate outside the very high frequency (VHF) band. 

• A variety of (somewhat divergent) views had been presented with regard to the future evolution 

of aeronautical mobile communications. 

• The universally recognized benefits of harmonization and global interoperability of air ground 

communications should not be forgotten when pursuing optimized local solutions. 

• The successful gradual introduction of data communications should be continued to complement 

and replace voice for routine communications. 

Based on these observations, several conference recommendations were made. These included 

• Recommendation 7/4—Investigation of future technology alternatives for air-ground 

communications. That ICAO 

– investigate new terrestrial and satellite-based technologies, on the basis of their potential for 

ICAO standardization for aeronautical mobile communications use, taking into account the 

safety-critical standards of aviation and the associated cost issues. 

• Recommendation 7/5—Standardization of aeronautical communication systems. That, for new 

aeronautical communication systems, ICAO 

– continue to monitor emerging communication systems technologies but undertake 

standardization work only when the systems meet all of the following conditions: 

ο can meet current and emerging ICAO ATM requirements 

ο are technically proven and offer proven operational benefits 

ο are consistent with the requirements for safety 

ο are cost beneficial 

ο can be implemented without prejudice to global harmonization of the CNS/ATM systems 

ο are consistent with the Global Air Navigation Plan for CNS/ATM Systems 

(Doc. 9750) 
NASA/CR—2008-214987 2

At ANConf/11, there was a strong request particularly from the airlines (International Air Transport 

Association) for international cooperation in order to achieve the stated objectives and goals in a 

harmonized and globally interoperable manner. In part to address the ICAO actions and recommendations 

above and in part to address frequency congestion and spectrum depletion in core Europe and dense 

United States airspace, the FAA and EUROCONTROL have embarked on a cooperative research and 

development program. The terms of this program are outlined in the Terms of Reference document for the 

program, which has been entitled “Future Communications Study (FCS)”. By agreement, joint FAA and 

EUROCONTROL research and development activities require terms of reference, which are referred to as 

“action plans” and are numbered sequentially. The Terms of Reference for the Future Communications 

Study are detailed in Action Plan 17 (AP–17), and NASA, the FAA, and EUROCONTROL all have 

defined roles in the research and development activities. 

1.2 Future Communication Study Technology Investigations 

The terms of reference for the FCS organized the work program into six technical and three business 

themes supporting the definition of a future globally interoperable communications system for air traffic 

management (ATM) operations in the timeframe of 2020 and beyond. Three of the technical themes 

address key activities relating to the identification of the most suitable technology candidates for the 

future communication infrastructure. These include (1) identification of requirements and operating 

concepts, (2) technology alternatives assessment, and (3) development of a future communications 

roadmap. 

The first theme has been addressed through the development of the Communications Operating 

Concept and Requirements (COCR) for the future radio system (FRS), a document which describes the 

future operating concepts and environment associated with safety and regularity of flight including air 

traffic services (ATS) and safety-related aeronautical operational control (AOC) communications. The 

document also describes the operational and communication requirements associated with the radio 

components of a communication system collectively referred to as FRS. The second theme applies the 

material captured in the COCR to perform a technology assessment. Specifically, the FCS terms of 

reference calls for “investigation of potential communications technologies operating inside the VHF 

band and outside the VHF band to support the long-term mobile communication operation concept 

considering terrestrial and satellite base infrastructure.” Finally, based on current and planned operational 

aeronautical communication systems both within core Europe and the United States, and considering 

results of the technology assessment, the final technical theme includes a definition of a communications 

roadmap that supports “planning for and achieving smooth transition” to recommended technologies. 

NASA was to provide the leading role in this effort. Specific investigations have been performed as a 

sequence of three study phases, Technology Prescreening (Phase I), Technology Screening and Indepth 

Studies (Phase II), and Additional Technologies and Investigations for Provision of Future Aeronautical 

Communications (Phase III). Interim reports associated with results of the first two study phases are 

available as follows: 

• Phase I (completed December 2004): “Technology Assessment for the Future Aeronautical 

Communications System,” NASA/CR—2005-213587, available at 

http://gltrs.grc.nasa.gov/reports/2005/CR-2005-213587.pdf

• Phase II (completed July 2006): “Identification of Technologies for Provision of Future 

Aeronautical Communications,” NASA/CR—2006-214451 (ref. 3), available at 

http://gltrs.grc.nasa.gov/reports/2006/CR-2006-214451.pdf

1.3 Stakeholder Inputs 

During the course of the FCS, interim findings were briefed to FAA and EUROCONTROL senior 

management, ICAO, industry, and to the United States Air Traffic Management Advisory Committee 
NASA/CR—2008-214987 3

(ATMAC). Significant feedback was received on some of the interim study results. Some raised concern 

on moving to a new communication band due to perceived cost ramifications of additional ground 

infrastructure and either additional hull penetrations or costly equipment integration on aircraft. ATMAC 

defined a set of recommendations that related to future aeronautical communication capability that 

included (ref. 1) 

• Sustain voice in VHF spectrum as long as possible, maintaining analog 25-kHz double side bandamplitude modulation (DSB–AM) until such time as spectrum pressures require reducing channel 

spacing to 8.33 kHz. 

• Pursue new technological solutions as a last resort. 

• Data link is important—commit to a technology and implement by 2015. 

• Keep AOC and ATS separate. 

The FAA indicated intent to comply with the ATMAC recommendations, but also a desire to prepare 

for the future. Should the capacity of the aeronautical VHF spectrum ever prove insufficient to provide 

the total data link capacity required, the FAA would support a new system to be ready and available to 

ensure that the aviation communications needs are accommodated. This is completely in line with the 

ICAO ANConf/11 observation that “This evolution would likely require the definition and 

implementation of new terrestrial and/or satellite systems that operate outside the VHF band.” This same 

theme was reflected by EUROCONTROL, which indicated that European focus is on consideration of an 

L-band system. EUROCONTROL also explored the potential of satellite systems, however initial 

analysis concluded that availability may preclude their use as a primary system in continental airspace. 

After feedback on Phase I results, subsequent FCS technology investigation focus has been made to 

support the understanding of issues associated with hosting a communications system in either L-band or 

C-band and with the potential use of satellites for flight critical communications in some airspace 

domains. 

Another significant set of comments on the Phase I results was received from the ICAO Aeronautical 

Communication Panel (ACP) at the working group of the whole meeting in June 2005. Feedback to the 

study team on the evaluation process and criteria from the ICAO ACP indicated the original scope of the 

FCS was too broad. Rather than specifying a technology that would meet all of the ATM communications 

requirements (including voice and data), it was recommended that the technology investigation focus on a 

data-only solution, keeping in mind that a future system would augment existing systems, not 

immediately replace them. Furthermore, the ACP indicated that the genesis of the original evaluation 

criteria (Phase I study criteria) was unclear. The panel asked that a set of evaluation criteria directly 

traceable to the COCR document be developed for the FRS, and that the technology screening process be 

repeated (ref. 2). 

All of the feedback influenced the direction of the study, helping to identify focus areas for indepth 

evaluations and tailoring the applied evaluation methodology. 

1.4 Approach Introduction and Overview 

As decision-making in the aeronautical environment can be complex, a structured methodology that 

accommodates stakeholder inputs has been defined and applied in the FCS. Specifically, a six-step 

methodology, as shown in figure 3, was defined and followed. The activities included in the methodology 

have been performed in three study phases, Technology Prescreening (Phase I), Technology Screening 

and Indepth Studies (Phase II), and Additional Technologies and Investigations for Provision of Future 

Aeronautical Communications (Phase III). 

The first set of activities in the defined evaluation process (steps 1A and 1B) included derivation of 

evaluation criteria and metrics. Addressing stakeholder direction, a structured analysis of the COCR was 

undertaken to ensure traceability of criteria to requirements. This structured analysis, along with 
NASA/CR—2008-214987 4

consideration of ICAO recommendations for future communication systems captured in consensus 

documentation, derived technical and viability evaluation criteria. 

Step 2 is to identify the most promising technology candidates. Over 50 technologies were considered 

in the technology screening process. The inventory included technologies collected through requests for 

information from NASA to industry; EUROCONTROL inputs from European manufacturers; and ICAO 

ACP WG–C member state inputs and represented technologies defined for current and planned 

commercial applications as well as standards and prototypes developed specifically for aviation. A 

screening process applied a small set of key technical and viability evaluation criteria at a high level. The 

output of this work was a subset of most promising technologies that would be subject to indepth analysis 

and further consideration in the future aeronautical communication infrastructure. 

The remaining steps in the evaluation process (steps 3 through 6) contribute to detailed assessment of 

the most promising candidate technologies. A concept of how the technology would be applied to the 

aeronautical environment described in the COCR was defined, followed by evaluation of a technology to 

the full complement of evaluation criteria. Supporting these steps was indepth analysis of the considered 

technologies. The process concludes with consideration of the relative importance of criteria and the use 

of this information to identify the best performing technology. 

1.5 Supporting Assessments 

A considerable number of indepth assessments were performed to support the technology evaluation 

process and to gain a better understanding of the applicability of the most promising technologies to the 

future aeronautical communication environment. Indepth studies were conducted as part of the FCS Phase 

II and Phase III study efforts. A full set of the indepth analyses is provided below in table I. Also 

indicated is a reference which identifies where the full study is documented. 

TABLE I.—FCS TECHNOLOGY INVESTIGATION INDEPTH STUDIES 

Topic 

no. 

Indepth study topic Location of study documentation 

(objectives, methodology, results) 

1 L-band Air/Ground Communication 

Channel Characterization 

FCS Phase II interim report (“Identification of Technologies for Provision 

of Future Aeronautical Communications,” NASA Report NASA/CR—

2006-214451, ITT Industries, July 2006), Section E.1.1 

2 Project-34/Telecommunication 

Industry Association (TIA) 902 Series 

Standards (P34/TIA–902) Technology 

Performance Assessment 

FCS Phase II interim report (“Identification of Technologies for Provision 

of Future Aeronautical Communications,” NASA Report NASA/CR—

2006-214451, ITT Industries, July 2006), Section E.1.2 and E.1.4 

3 P34/TIA–902 Technology Intellectual 

Property Assessment 

Section 4 

4 L-band Digital Link (LDL) 

Technology Performance Assessment 

FCS Phase II interim report (“Identification of Technologies for Provision 

of Future Aeronautical Communications,” NASA Report NASA/CR—

2006-214451, ITT Industries, July 2006), Section E.1.3 and E.1.4 

5 Wideband Code Division Multiple 

Access (WCDMA) Functional 

Assessment 

Section 3 

6 L-band Technology Cost Assessment 

for Ground Infrastructure 

FCS Phase II interim report (“Identification of Technologies for Provision 

of Future Aeronautical Communications,” NASA Report NASA/CR—

2006-214451, ITT Industries, July 2006), Section E.1.8 

7 L-band Interference Testing Section 2 

8 Satellite Technology Availability 

Performance 

FCS Phase II interim report (“Identification of Technologies for Provision 

of Future Aeronautical Communications,” NASA Report NASA/CR—

2006-214451, ITT Industries, July 2006), Section E.2 

9 IEEE 802.16e Performance 

Assessment in Aeronautical C-band 

Channel 

FCS Phase II interim report (“Identification of Technologies for Provision 

of Future Aeronautical Communications,” NASA Report NASA/CR—

2006-214451, ITT Industries, July 2006), Section E.3 

 
NASA/CR—2008-214987 5

2.0 L-Band Interference Measurements 

This section of the report describes one of the indepth analyses conducted during FCS Phase III. Four 

major sections document the work: background, methodology, results, and conclusions. The background 

section describes the motivation, objective, and approach for this study and provides a brief overview of 

the distance measuring equipment (DME) system. The methodology section describes the test setup, test 

equipment, test cases, and waveform development process. The results section presents plots of the 

measurement data and explains how the data should be interpreted. The conclusions section describes 

how the data should be applied towards the technology evaluations and also suggests additional tests that 

would build upon this work and improve understanding of the L-band interference environment. 

2.1 Background 

ICAO is considering the use of L-band (960 to 1024 megahertz (MHz)) to employ the next generation 

aeronautical communication system. In order to assess the viability of proposed communication systems 

in this frequency band, the interference potential from FRS candidates to systems already utilizing this 

spectrum must be characterized. An interference measurements campaign was defined for Phase III of the 

FCS to better our understanding of the interference environment in L-band. ITT, with the help of the Ohio 

University Avionics Engineering Department, conducted interference measurements against DME for 

three FRS candidate technologies: WCDMA, LDL, and P34. 

2.1.1 Motivation 

The DME system is a vital navigation tool used to ensure flight safety. Before any new 

communication systems can be allowed to share spectrum with DME, a compatibility analysis must be 

performed to assess potential degradation of DME system performance. A compatibility analysis of a 

FRS with DME in L-band involves many potential interference scenarios, including cosite (onboard the 

aircraft), air-to-air, air-to-ground/ground-to-air, and ground-to-ground (ref. 4). These various scenarios 

are illustrated in figure 4.

For this interference measurement study, the cosite interference scenario is emulated. The cosite 

interference scenario serves as a guide for specifying the bounds of interference power used when taking 

measurements. The signal levels used for interference measurements should encompass the power ranges 

that will be seen in practice, and these levels are greatest in the cosite scenario. This is not to say that 

ground stations do not also transmit high power signals, but ground stations are generally separated by 

large distances to mitigate interference effects. Antennae onboard the aircraft do not have this liberty. 

Figure 5 illustrates the cosite scenario. 

 
NASA/CR—2008-214987 6

2.1.2 Objective 

The objective of this study is to determine the extent and nature of interference to DME airborne 

receivers by FRS candidate technology waveforms. This study focuses only on the susceptibility of 

interference to existing airborne avionics. This study does not focus on interference from DME to FRS 

airborne avionics, as L-band FRS receivers do not yet exist. 

The three FRS candidate technologies selected for this interference study are WCDMA, LDL, and 

P34. All three technologies scored well in the prescreening and screening stages conducted during Phases 

I and II of the FCS (ref. 5). WCDMA scored highest out of the cellular telephony technology family. LDL 

scored highest out of the custom narrowband technology family. P34/TIA–902 scored highest out of the 

public safety radio technology family. In addition to representing their respective technology families, 

WCDMA, LDL, and P34, also use fundamentally different waveform structures: ultrawideband, 

narrowband, and orthogonal frequency division multiplexing (OFDM), respectively. 

2.1.3 Approach 

The overall approach for the interference measurements study consists of six interrelated tasks. Task 

1 consists of generating a test plan that contains test procedures for each test case in the study. Task 2 

consists of specifying the interference sources to be used for this study. Task 3 consists of procuring test 

equipment to emulate FRS transmitters. Task 4 consists of conducting bench tests against the DME 

receivers. Task 5 consists of analyzing and reducing the measurement data. The sixth task consists of 

documenting the study and presenting results in a report. The flow of these tasks is illustrated in figure 6. 

2.1.4 DME System Overview 

The DME system is a navigational aid that provides slant range distance to aircraft. The system 

consists of airborne equipment and ground-based equipment, which are called interrogators and 

transponders, respectively. The interrogator transmits paired pulses to the transponder which replies with 

its own paired pulse message. The interrogator measures the time elapsed between its own transmission 

and reception of the transponder’s response, which is then used to calculate the slant range distance. 

Figure 7 illustrates this concept. 
NASA/CR—2008-214987 7

The DME system operates in the frequency band 960 to 1215 MHz. The interrogation and reply 

frequencies are always offset by 63 MHz. The entire band allows 126 channels for interrogation and 126 

channels for transponder replies. Interrogations are sent on frequencies 1025 to 1150 MHz. Replies from 

the transponders are sent on frequencies 962 to 1024 MHz and 1151 to 1213 MHz. DME channels are 

spaced 1 MHz apart on center, with bandwidths of 0.5 MHz. 

2.2 Methodology 

The basic methodology for characterizing interference susceptibility is to observe the response of the 

DME interrogator in the presence of the interfering signals. The interfering waveforms are injected into 

the system at various frequency separations, and the signal levels are incrementally adjusted in order to 

determine the power thresholds that induce a standard response from the device under test (DUT). 

For DME, the standard response is described by two metrics: acquire stable operating point (ASOP) 

and break stable operating point (BSOP). ASOP is defined as the maximum interfering signal level where 

the DME interrogator consistently locks on and provides bearing, ident, and range information. BSOP is 

defined as the minimum interfering signal level that causes the DME interrogator to lose lock by failing to 

provide bearing, ident, or range information. These definitions are reiterated below in table II. 

TABLE II.—ASOP AND BSOP DEFINITIONS (ref. 6) 

DME standard response metrics Definition 

ASOP Desired signal level at which bearing, ident, and range lock on consistently 

BSOP Desired signal level at which either bearing, ident, or range breaks lock 

2.2.1 Test Setup and Equipment 

The test setup for the interference measurements is illustrated in figure 8. Interrogations are sent from 

the DME interrogator to the DME test set. The DME test set replies to interrogations with a DME reply 

signal. The DME reply signal is coupled with the interference signal, and the DUT is observed. The 

interference signal undergoes bandpass filtering before it is coupled with the DME reply signal. This 

reduces transmitter broadband noise that is produced by the vector signal generator. The spectrum 

analyzer allows test engineers to observe spectrums of the signals in the system. Detailed descriptions of 

these devices follow the test setup diagram. 
NASA/CR—2008-214987 8

The DUT for this study is the DME interrogator. The make and model that was tested is the BF 

Goodrich Flights Systems TX–670 DME Transceiver (BF Goodrich). Ideally, models from various 

manufacturers would be studied to develop a performance range, but testing of additional interrogators 

was not possible in the context of this study. The TX–670 unit is a cabin-class DME interrogator. This 

particular DME interrogator has been used in a variety of FAA-sponsored DME tests conducted by Ohio 

University including design approval tests of DME ground stations. 

The ground-based transponder is emulated by the Aeroflex IFR–6000 Ramp Test Set (Aeroflex). This 

multimode test is designed to test avionics from various systems, including DME. The IFR–6000 both 

receives and replies to interrogations, while providing insight into the current state of the interrogator 

through a real-time display screen. Several useful status parameters such as DME reply signal level and 

pulse repetition frequency (PRF) are displayed and updated during testing. 

The interference source is emulated by an Agilent E4438C Vector Signal Generator (Agilent). This 

device allows users to create waveform files in software and then upload those waveform files to the 

signal generator for playback. Four options for the vector signal generator were purchased to facilitate 

testing. Option 005 includes a 6-GB internal hard drive for storing waveform files. Option 502 offers the 

ability to transmit up to 2 GHz. Option 602 includes baseband signal generation capabilities. Option 400 

includes the WCDMA personality, which is described in more detail in Section 2.2.3. 

The filter used in the test setup is a Trilithic tunable bandpass filter (model number: 5VF–750/1500–

1–50–KK) (Trilithic). Results from the first pass of interference measurements indicated the presence of 

transmitter broadband noise in the interference signals. The broadband noise was indistinguishable from 

the noise floor of the spectrum analyzer during waveform validation. Discussions with the equipment 

manufacturer verified that the noise floor is attributable to excess quantization noise in the vector signal 

generator, and the only way to reduce the noise floor was with additional filtering. The additional filtering 

reduces the noise floor, which results in a more realistic spectrum that one would expect from actual 

transmitter implementation. Figure 9 shows the filter response to a sine wave sweep when centered at the 

chosen test frequency, 966 MHz. The filter response shows a passband of about 12 MHz and provides at 

least 37 dB of attenuation only 10 MHz away from the passband. The insertion loss of the filter and 

associated cables totals 2.5 dB. 
NASA/CR—2008-214987 9

The personal computer interfaces with the interrogator via a software program. The program collects 

and displays status data during testing. This data, which includes bearing, ident, and range, is used to 

determine if the interrogator has acquired or broken lock. The software stores the data from each trial into 

a unique file for postprocessing. 

The make and model of the spectrum analyzer is Hewlett Packard 8591E (Hewlett Packard). The 

spectrum analyzer is used to capture spectrum plots of the signals in the system. 

2.2.2 Test Cases 

Four major test cases comprise the interference measurements study. The test procedures for each of 

these test cases were derived from measurement procedures outlined in MIL–STD–449D (ref. 7). Below 

are descriptions and general procedures for each test case. 

2.2.2.1 Receiver Sensitivity Test 

The purpose of the receiver sensitivity test is to determine power thresholds of the DME reply signal 

that induce a standard response from the DME interrogator in the absence of an interference signal. To 

start, the DME reply signal level is set very low (~ –100 dBm) so that the DME interrogator cannot 

achieve lock. Using the DME test set, the DME reply signal level is incrementally increased until the 

DME interrogator achieves lock. Next, the DME reply signal level is incrementally decreased until the 

DME interrogator breaks lock. This test characterizes the hysteresis of acquiring and breaking lock of the 

receiver. 

2.2.2.2 Transmission Emission Spectrum Test 

The purpose of the transmission emission test is to capture the power vs. frequency characteristics of 

the interference waveforms. During this test the interference source is connected directly to the spectrum 

analyzer, and the frequency spectrum is saved to disk. 
NASA/CR—2008-214987 10

2.2.2.3 Co-Channel Interference Test 

The purpose of the co-channel interference test is to determine ASOP and BSOP for the interfering 

waveforms when they are tuned to the same frequency as the DME interrogator. To start, the DME reply 

signal level is set to 3 dB above receiver sensitivity, and the interfering signal level is incrementally 

adjusted until ASOP and BSOP are found. The test is repeated for higher DME reply levels (in 10-dB 

increments) until a DME reply level close to –50 dBm is reached. 

2.2.2.4 Adjacent Channel Interference Test 

The purpose of the adjacent channel interference test is to determine ASOP and BSOP for the 

interfering waveforms at various frequency separations from the DME tuned frequency. To start, the 

DME reply signal level is set to 3 dB above receiver sensitivity, and the interfering signal level is set as 

high as possible. The vector signal generator used during this study has a maximum power output of 

20 dBm (9.57 dBm after insertion losses). With the interference power maxed out, the frequency of the 

interference source is tuned far enough away such that the DME interrogator can acquire lock. Next, the 

frequency separation is incrementally decreased until the DME interrogator breaks lock. The frequency 

separation where the interrogator loses lock is defined as Δf. Next, ASOP and BSOP are determined at 

frequency separations of Δf, 1⁄2Δf, 1⁄4Δf, etc. until the frequency separation is within the 3 dB bandwidth of 

the DME signal. The data from the co-channel and adjacent channel tests are plotted as sets of ASOP and 

BSOP curves for various DME reply levels. 

2.2.3 Waveform Development 

L-band transmitters do not exist for the three FRS candidate technologies tested, so these waveforms 

must be emulated by test equipment. The vector signal generator procured offers various solutions for 

developing these waveforms. The waveform development process for each of the FRS candidate 

technologies tested in this study is described below. 
NASA/CR—2008-214987 11

2.2.3.1 WCDMA Waveform Development 

Option 400 for the E4438C vector signal generator is the WCDMA personality. This personality is a 

preloaded waveform used by industry to test user and base station equipment for the WCDMA standard. 

No additional tailoring of this waveform was required. Figure 10 shows the emission spectrum of the 

WCDMA waveform whose bandwidth is 5 MHz. 

2.2.3.2 LDL Waveform Development 

No waveform personality exists for LDL so the LDL waveforms are developed using MATLAB and 

Simulink.1

 A transmitter model for LDL was created in Simulink in accordance with the published 

documentation (ref. 8). The model produces a complex baseband representation of the waveform. The 

waveform is formatted so that it can be uploaded to the vector signal generator. Agilent offers a free 

MATLAB library that transfers formatted waveforms to the signal generator. Once transferred, the 

waveform segments can be looped to play for as long as is required. Figure 11 shows the Simulink model 

used to generate the LDL waveforms. 

Two versions of the LDL waveform are modeled for the interference measurements study. The first is 

a gated LDL waveform. The gating structure was modeled after the “Simple LDL Time Slot Structure” 

described in the June 2005 paper “An L-band Digital Communications Link Concept for Air Traffic 

Control” by Dr. Warren J. Wilson. The time slot is 30 μs in duration and contains 1875 bits. The time slot 

is composed of four segments in the following order: a 72-bit M-burst, a 589-bit guard period, a 

624-bit V/D-burst, and a 590-bit guard period. A mask that uses this structure is applied to the waveform 

to achieve the gating mechanism. Figure 12 shows a plot of the mask where the abscissa is scaled to 

waveform samples (187 500 samples total). 

The overall duty cycle of the gated LDL waveform is 37.12 percent. The second LDL waveform 

modeled is a continuous waveform whose duty cycle is 100 percent. Figure 13 shows the transmission 

emission spectrum of the continuous LDL waveform. 

 

1

 MATLAB and Simulink are registered trademarks of The Mathworks. 
NASA/CR—2008-214987 12

2.2.3.3 P34/TIA–902 Waveform Development 

For this assessment, the P34/TIA–902 ground station waveform (continuous) was modeled. The 

aircraft station waveform, which is a gated waveform, was not modeled in this assessment. Therefore, the 

results of the P34/TIA–902 measurements can be considered an upper bound on interference or can be 

used for assessment of the intersite interference scenario. The P34/TIA–902 waveform development 

process was the same as used for LDL, with the exception of the gating mechanism. Figure 14 shows the 

transmitter model for P34. 
NASA/CR—2008-214987 13

Each mode of P34/TIA–902 (50-, 100-, and 150-kHz) has its own Simulink model, but only the 50-

kHz is shown. All of the P34/TIA–902 waveforms are modeled as continuous transmissions (100 percent 

duty cycle). Figure 15 shows the transmission emission spectrum of the 50-kHz mode of P34. 

Figure 16 shows the transmission emission spectrum of the 100-kHz mode of P34. 
NASA/CR—2008-214987 14

Figure 17 shows the transmission emission spectrum of the 150-kHz mode of P34. 
NASA/CR—2008-214987 15

2.3 Measurement Results 

This section is organized by waveform and begins with a discussion of the expected undesired power 

levels at the DME receiver. Next, ASOP and BSOP charts show the actual measurements. The charts are 

followed by a discussion of how they should be interpreted. In general, the ASOP and BSOP charts in this 

section contain data from the both filtered and unfiltered trials. Specifically, any data for frequencies 

greater than or equal to 980 MHz or any data for frequencies less than or equal to 952 MHz use the filter. 

Likewise, any data from frequencies greater than 952 MHz, but less than 980 MHz do not use the filter. 

Complete datasets for the unfiltered measurements can be found in appendix A. 

In an attempt to minimize confusion when reviewing the results, some questions been addressed here. 

• Which plot is the author talking about, ASOP or BSOP? The discussions that follow the 

charts speak to the ASOP charts. The purpose of this interference study is to determine the 

maximum interference levels at which the DME can acquire lock, not break lock. 

• Why are the plots not left-right symmetrical about 966 MHz? The DME receive band spans 

960 to 1215 MHz and the selectivity of the DME interrogator attenuates the signals outside of this 

band. Often times data from frequencies less than 966 MHz appears to be shifted upwards. The 

test frequency, 966 MHz, was chosen to pick up this selectivity. 

• Why is there no data below 966 MHz? In order to have enough time to collect at least some 

data for all of the waveforms, some of the datasets do not have data from below 966 MHz. The 

most important data is in the DME band: 960 to 1215 MHz. 

• As the frequency separation increases in the ASOP plots, why do data points seem to 

eventually converge to 9.57 dBm? Also, why does it look like data is missing from some of 

the BSOP plots? These two questions describe the same scenario. For some of the interference 

waveforms, especially at large frequency separations, the maximum power of the signal generator 

is not enough to cause the DME to break lock. In these instances, 9.57 dBm is recorded for ASOP 

since the DME can acquire at maximum power. Likewise, the corresponding point in the BSOP 

plot spears to be missing because an actual BSOP could not be determined. In reality the ASOP 

value might be higher than 9.57 dBm. 

• Why is there a gap in the data between 952 and 980 MHz? If no data exists between 952 and 

980 MHz, then only filtered trials were conducted for that waveform. If data does exist in this 

range, then that data is from unfiltered trails. 

2.3.1 WCDMA/DME Interference Measurements 

Link budgets for a representative FRS WCDMA implementation indicate a transmit powers on the 

order of 33 dBm (ref. 9). Typical values of isolation for antennae on the same side of the aircraft range are 

25 to 35 dB. Using an optimistic value of 35 dB for isolation, the resultant undesired power at the DME 

receiver is –2 dBm. This value is important when interpreting the measurements shown in figure 18. Note 

that the cosite power level is shown on the figure; the DME received signal level should be above this line 

for DME operations (ASOP). For reference (as the WCDMA ground station transmitter has a similar 

waveform to what has been modeled for an aircraft transmitter, and assuming an aircraft 1000 ft above a 

ground transmitter), an intersite interference reference power level is also noted in figure 18. 

The measurements show that the DME interrogator breaks lock for WCDMA signal levels less than 

what is expected on the aircraft. This phenomena occurs even at large frequency separations. It is not until 

the interference signal is tuned 50+ MHz away from the DME where all of the ASOP curves are above 

the expected power threshold of –2 dBm. The WCDMA waveform tested in this study has a 100 percent 

duty cycle. 
NASA/CR—2008-214987 16

2.3.2 LDL/DME Interference Measurements 

Link budgets for LDL in a FRS implementation indicate transmit power levels on the order of 

40 dBm. Again, using an optimistic value of –35 dB for antenna isolation, the resultant undesired power 

at the DME receiver is 5 dBm. Figure 19 shows the results for the nongated LDL waveform. 

The measurements show that the DME interrogator breaks lock for nongated LDL signal levels less 

than what is expected on the aircraft. This phenomenon occurs even at large frequency separations. It is 

not until the interference signal is tuned 50+ MHz away from the DME where all of the ASOP curves are 

above the expected power threshold of 5 dBm. 
NASA/CR—2008-214987 17

LDL uses very high frequency digital link 3 standard for protocols layers above the physical layer, 

including a gated/time division multiple access (TDMA) framing structure. This suggests that a duty 

cycle far less than 100 percent might be expected in practice. A gated version of the waveform was also 

tested; figure 20 shows the results for the gated LDL waveform. As in the WCDMA results, the graph 

below includes the cosite interference reference line and the intersite interference reference line 

(assuming an aircraft 1000 ft above a ground transmitter). The intersite reference is applicable as the LDL 

ground radio may have similar waveform and/or duty cycle as the aircraft transmitter. 

The gated version did not cause the DME to break lock for filtered trials and the DME was able to 

acquire lock under maximum interference conditions (test frequencies off-tuned by 10+ dB). Almost all 

of the filtered ASOP values were recorded as 9.57 dBm, inferring that the ASOP values are actually 

higher than 9.57 dBm. The effect of gating makes the DME much more tolerant of this waveform. This 
NASA/CR—2008-214987 18

suggests that interference susceptibility is related to the average power of the interferer. This was the only 

gated waveform tested during this study, and the results for it were the most positive. Filtered results near 

the tune frequency of the DME suggested off-tuning may still be required for LDL. 

2.3.3 P34/DME Interference Measurements 

Link budgets for a representative P34/TIA–902 implementation suggest a similar transmit power to 

LDL can be used (on the order of 40 dBm). Considering a cosite scenario (not completely applicable as 

the modeled waveform was for the P34/TIA–902 ground stations) and applying an optimistic value of 

–35 dB for antenna isolation, the resultant undesired power at the DME receiver is 5 dBm. For an intersite 

scenario, more applicable for this modeled waveform, assuming that an aircraft is 1000 ft above the 

transmitting ground radio, the path loss is on the order of 83 dB and thus the resultant undesired power at 

the DME receiver is –43 dBm. Figure 21 shows the results for the 50-kHz mode of P34/TIA–902 

(constant transmission). 
NASA/CR—2008-214987 19

The measurements show that the DME interrogator breaks lock for the P34/TIA–902 (50 kHz) signal 

levels less than what is expected on the aircraft (assuming unrealistic 100 percent duty-cycle model). This 

phenomena occurs even at large frequency separations. It is not until the interference signal is tuned 

50+ MHz away from the DME where all of the ASOP curves are above the expected power threshold of 

5 dBm. These results are similar to the results from the nongated LDL waveform and some inferences can 

be made. Reducing the duty cycle for the LDL waveform improved the performance of the DME 

significantly. The duty cycle of P34/TIA–902 in practice is surely to be less than the 100 percent duty 

cycle tested during this study. It is recommended that additional tests be conducted to experiment with 

duty cycle for this waveform. 

For the intersite scenario, when the interference signal is tuned approximately 1 to 2 MHz away from 

the DME, the ASOP curves are above the expected power threshold of 5 dBm. These results are very 

promising for compatibility. 
NASA/CR—2008-214987 20

Figure 22 shows the results for the 100-kHz mode of P34. Note that only filtered trials (for frequencies 

less than 952 MHz and greater than 980 MHz) were collected for this scenario. 

Similar to the 50-kHz results, the measurements show that the DME interrogator breaks lock for the 

P34/TIA–902 (100 kHz) signal levels less than what is expected on the aircraft (assuming unrealistic 

100 percent duty-cycle model). This phenomena occurs even at large frequency separations. It is not until 

the interference signal is tuned 50+ MHz away from the DME where all of the ASOP curves are above 

the expected power threshold of 5 dBm. Like the 50-kHz version of P34, these results are similar to the 

results from the nongated LDL waveform and some inferences can be made here, too. Reducing the duty 

cycle for the LDL waveform improved the performance of the DME significantly. As noted previously, 

the duty cycle of P34/TIA–902 in practice is surely to be less than the 100 percent duty cycle tested 

during this study. We recommend that more tests be conducted that experiment with duty cycle for this 

waveform. Note, that testing results for the intersite scenario, the fully applicable scenario for the 
NASA/CR—2008-214987 21

continuous P34/TIA–902 waveform, were not conducted for the 100-kHz bandwidth. It is anticipated, 

however, that results similar to the 50-kHz channel would be achieved. 

Figure 23 shows the results for the 150-kHz mode of P34. Note that only filtered trials (for 

frequencies less than 952 MHz and greater than 980 MHz) were collected for this scenario. 

Once more, the measurements show that the DME interrogator breaks lock for the P34/TIA–902 

(150 kHz) signal levels less than what is expected on the aircraft (assuming unrealistic 100 percent dutycycle model). This phenomena occurs even at large frequency separations. It is not until the interference 

signal is tuned 50+ MHz away from the DME where all of the ASOP curves are above the expected 

power threshold of 5 dBm. Like the 50- and 100-kHz versions of P34, these results are similar to the 

results from the nongated LDL waveform and the inferences as noted earlier can be made here, too. Note, 

that testing results for the intersite scenario, the fully applicable scenario for the continuous P34/TIA–902 

waveform, were not conducted for the 150-kHz bandwidth. 
NASA/CR—2008-214987 22

2.4 Conclusions and Future Work 

This study provides an improved understanding of the interference environment associated with 

DME. While limitations in the test equipment do not provide enough information to address specific 

channelization techniques for FRS candidates, the interference measurements do suggest that the addition 

of an FRS in the DME band may be feasible. Three major findings of the interference measurements 

study are as follows: 

• The power levels expected from continuously transmitting FRS equipment onboard the aircraft 

may be sufficiently high as to cause desensitization in the DME interrogator. This phenomenon 

was evident for all of the FRS candidates even at large frequency separations for the DME that 

was tested. This finding is not favorable for FRS candidate technologies whose concept of use 

assumes continuous transmissions (e.g., WCDMA). 

• The data also indicates that the DME interrogator is more tolerant to gated transmissions (i.e., 

there is potential for implementation of a technology with a gated waveform; but offset channels 

may still be required (to be investigated)). A majority of the measurements used 100 percent duty 

cycles, which results in a conservative analysis. Lesser duty cycles may be expected in practice. It 

is expected that low-to-moderate duty cycles will interfere less with DME compared to FRSs with 

high duty cycles. This finding may be favorable for FRS candidate technologies whose concept of 

use assumes noncontinuous transmissions (i.e., LDL and P34/TIA–902 (partial)). 

• Further analysis should be conducted to characterize the relationship between FRS duty-cycle and 

interference susceptibility (the duty cycle investigation should include more variables than just 

overall duty cycle; there may be some combination of specific timescales of on/off pulses and 

overall duty cycle that results a seemingly “invisible” waveform from the DME interrogator’s 

perspective); in the context of this investigation, identification of collocation constraints can also 

be investigated. It is also recommended that different models of DME interrogators be tested to 

provide a range of performance. 

The interference measurements, in conjunction with the concept of use defined for each candidate 

FRS technology, were used to support the detailed technology evaluations in this study. It is 

recommended that prototype FRS transmitters be developed to facilitate additional technology 

evaluations and/or modifications and to help define specific channelization techniques. 
NASA/CR—2008-214987 23

3.0 WCDMA Functional Assessment 

Detailed technology analyses conducted as part of the FCS Phase III effort focused on two of the 

candidate FRS solutions (to complement previous indepth assessments). Specifically, one of the 

technologies and analysis areas addressed is to perform functional analysis of WCDMA services, create 

mapping of COCR services to WCDMA services/functions, and trace protocol interactions. 

WCDMA is a direct spread, wideband frequency division, duplex code division multiple access 

(CDMA) standard developed by 3GPP (Third Generation Partnership Project). WCDMA was selected as 

the air interface for the Universal Mobile Telecommunications System (UMTS), the 3G successor to 

GSM (Global System for Mobile communication). WCDMA promises high data speeds to mobile and 

portable wireless devices. 

WCDMA is one of the technologies emerging from the FCS screening process as a promising FRS 

technology candidate. Previous detailed studies of this technology have investigated the performance of 

WCDMA to COCR service requirements and compatibility of this technology with existing aeronautical 

systems in L-band. This study of the COCR service provision in WCDMA provides another perspective 

of how to apply this technology to aeronautical systems. 

3.1 Objective 

The objective of this WCDMA study is to perform a functional analysis of the technology and 

identify how it can be used to support COCR services. Results of this analysis are used to determine the 

necessary elements of the architecture and protocol stack required to provision COCR services, which 

further supports the assessment of cost, certification, and standardization impact for applying WCDMA in 

aeronautical applications. 

3.2 Approach 

The overall approach applied for the WCDMA study consists of four steps. First, examine WCDMA 

network architecture, protocols and functions based on UMTS WCDMA network architectures and 3GPP 

technical specifications (ref. 10). Second, select COCR air traffic data link services for consideration 

based on the COCR and Radio Technical Commission for Aeronautics (RTCA)/DO–290 (ref. 11) 

documents. Third, map selected data link services to WCDMA network functions. Finally, results are 

documented in step 4. The flow of these tasks is illustrated in figure 24. 
NASA/CR—2008-214987 24

3.3 WCDMA Network Architecture 

As shown in figure 25, a WCDMA network consists of three interacting domains: Core Network 

(CN), WCDMA UMTS Terrestrial Radio Access Network (UTRAN) and user equipment (UE). The 

UTRAN provides the air interface access method for UE. The radio base station is referred to as Node-B, 

and control equipment for Node-Bs is called the Radio Network Controller (RNC). The main functions of 

the core network are to provide switching, routing, and transit for user traffic. The core network also 

includes the databases and network management functions. The core network is divided in circuit 

switched (CS) and packet switched (PS) domains. Some of the CS elements are mobile switching center 

(MSC), visitor location register (VLR), and gateway MSC. Packet switched elements are serving GPRS 

support node (SGSN) and gateway GPRS support node (GGSN). Some network elements, like equipment 

identity register (EIR), home location register (HLR), VLR, and authentication center (AuC) are shared 

by both domains. The PS domain can connect to the internet or packet data network (PDN). 

The WCDMA basic network function hierarchy is listed as follows: 

• Access network 

– Finding access point 

– Localize user equipment 

– Establish connectivity for signaling 

– Registration + Authentication and Authorization 

• Route/transfer data 

– Establish connectivity for data transfer (packet data protocol (PDP) context activation) 

– Routing 

– Address translating 

– Encryption and decryption 

– Compression 

– Resource management 

• Detach from the network 

– PDP context deactivation 

• Mobility management 

– Location management 
NASA/CR—2008-214987 25

The PDP context activation function provides information to support packet delivery between a UE and 

the network. The PDP deactivation function results in deletion of PDP context information at RNC and SGSN. 

Mobility management is the means by which a mobile network can keep track of the mobile subscriber 

location while connected to the network. The main function of mobility management is location management. 

In WCDMA, a group of cells is called a routing area (RA). The SGSN controls a service area containing 

several RAs. There are four location management procedures as shown in figure 26.

1. Cell Update—A UE informs the network of its current cell location. 

2. Inter-Node B/Intra RNC/Intra-SGSN—A UE changes to a cell of different Node B but remains in 

the same RNC and SGSN service area. 

3. Inter-SGSN Routing Update—Entry of a UE to a new RA triggers a change of SGSN service area. 

4. Inter-RNC/Intra-SGSN Routing Update—A UE changes RA and triggers a change of RNC but 

remains serviced by the same SGSN. 

3.4 Selection of Air Traffic Data Link Services 

A set of air traffic data link services is selected for the analysis. These services support the 

implementation of aeronautical communications and are used to identify required WCDMA protocol and 

functional elements. 

3.4.1 Sources of Service Information 

Two sources of service information were used in the analysis: COCR as the primary source and 

RTCA/DO–290 as a secondary source of service descriptions. The COCR includes a complete set of FRS data 

link service definitions including service descriptions and operational context. RTCA/DO–290 is an older 

document that was defined to provide the minimum requirements for air traffic data link services in continental 

airspace. Some of the services described in RTCA/DO–290 were the basis for service definitions in the COCR. 

RTCA/DO–290 provides service transaction details beyond what is provided in the COCR such as operational 

methods, sequence diagrams, abnormal events, safety, performance, etc. 

Figure 27 shows the COCR services organized into three major categories: ATS, AOC, and Network 

Management. For this study, the selection of data link services is focused on the ATS category, 

particularly on services that are also defined in the RTCA/DO–290 with more detailed descriptions.2

 This 

selection of ATS services correlating with services defined in RTCA/DO–290 is shown in red text in 

figure 27. These services include data link initiation capability (DLIC), air traffic control clearance 

message (ACM), air traffic control clearance (ACL), ATC microphone check (AMC), departure clearance 

(DCL), downstream clearance (DSC), digital-automatic terminal information service (D–ATIS), and 

flight plan consistency (FLIPCY). Full names of these services along with service dependencies are 

shown in figure 28. Here the DLIC service can be seen to be a prerequisite for all other services. 

 

2

Although the envisioned details for the FRS services defined in the COCR with the same name as the DO–290 

services may be different, the service descriptions in DO–290 was still considered generally applicable and was used 

for this assessment. 
NASA/CR—2008-214987 26
NASA/CR—2008-214987 27

3.4.2 Mapping Services Into WCDMA Network Functions 

The identified COCR services for consideration in this study are intended to be part of a future 

CNS/ATM implementation. Figure 29 (adopted from RTCA/DO–290) provides an overview of the 

CNS/ATM elements. These elements include the aircraft system, the air traffic service provider (ATSP) 

end systems, and the data link elements. Data link service elements may contain third-party 

communication services. 

3.4.3 Logical Mapping 

To provide a user's view of both the CNS/ATM elements and WCDMA network elements, a logical 

mapping of the two is provided as shown in figure 30. Here WCDMA network elements UE; 

UTRAN/RNC and Core network (PS domain); and PDN are mapped to Aircraft System Element; 

Interface to ATSP Communication Services/ATSP Communication Services; and Air Traffic Services 

Unit (ATSU), respectively. An air traffic context is also shown to reflect the potential application of 

WCDMA in CNS/ATM context. 

3.5 Service Mapping 

High level WCDMA network functions and DLIC service and its functions are described in further 

detail in this section. As noted previously, a set of eight COCR services was selected for the analysis. 

Although all eight services and functions are mapped into WCDMA interactions, as a representative 

example, only the mapping of DLIC service in WCDMA context is presented and explained in detail. 

Mapping results of the remainder of the data link services are presented only in terms of the service 

operational context and interaction sequences (app. B). 

3.5.1 Logical Mapping 

To provide a user's view of both the CNS/ATM elements and WCDMA network elements, a logical 

mapping of the two is provided as shown in figure 30. Here WCDMA network elements UE; 

UTRAN/RNC and Core network (PS domain); and PDN are mapped to Aircraft System Element; 

Interface to ATSP Communication Services/ATSP Communication Services; and 
NASA/CR—2008-214987 28

ATSU, respectively. An air traffic context is also shown to reflect the potential application of WCDMA in 

CNS/ATM context. 

3.6 Service Mapping 

High level WCDMA network functions and DLIC service and its functions are described in further 

detail in this section. As noted previously, a set of eight COCR services was selected for the analysis. 

Although all eight services and functions are mapped into WCDMA interactions, as a representative 

example, only the mapping of DLIC service in WCDMA context is presented and explained in detail. 

Mapping results of the remainder of the data link services are presented only in terms of the service 

operational context and interaction sequences (app. B). 

3.6.1 DLIC Service 

The DLIC service is used to uniquely identify aircraft. The DLIC service exchanges information 

between an aircraft and an ATSU to support other data link services. The DLIC provides version and 

address information for all data link services including itself and this service is executed prior to any other 

data link services. The three functions of DLIC are 

Initiation.—Exchange information and provide flight data to an ATSU. This function is between an 

aircraft and an ATSU. Information for other ATSU (up to eight) maybe exchanged. 

Contact.—An ATSU provides the DLIC address of a specific ATSU to an aircraft and requests the 

initiation function be performed between the aircraft and the specified ATSU. 

Update.—An ATSU provides its updated initiation information to an aircraft. The ATSU may update 

the information for other ATSUs when the ATSU has such initiation information. 

The three DLIC functions exchanged between a moving aircraft and multiple ATSUs are illustrated in 

figure 31 (from RTCA/DO–290). 
NASA/CR—2008-214987 29

3.6.2 DLIC to WCDMA Services 

Based on assessment of the WCDMA protocol, in order to provide DLIC capabilities, the following 

WCDMA network elements are needed: UE (aircraft end system), UTRAN/RNC, SGSN, HLR, GGSN, 

and ATSU End System. Sequence diagrams that illustrate the interactions among these elements are 

shown in figures 32 and 33, in which columns represent the necessary WCDMA elements and rows 

represent the three high level network functions exercised: 

• Access Network function, which further includes the Find Access Point, Localize UE, Setup Radio 

Resource Control (RRC), and Registration with security functions 

• Route/Transfer Data function (contains the PDP Context Activation and data transfer functions) 

• Detach Network function (contains the PDP deactivation function) 
NASA/CR—2008-214987 30
NASA/CR—2008-214987 31

WCDMA specific services that support aircraft movement through the ATC system have also been 

examined. Four operational scenarios were identified and mapped to aircraft movement scenarios. 

Figure 34 shows these four operational scenarios. Scenario I is when an aircraft moves within the same 

Node B range; Scenario II is when the aircraft moves across different Node B but still within the same 

RNC service area; Scenario III is when the aircraft moves across different RNCs but within the same 

SGSN area; Scenario IV is when the aircraft moves across different SGSN and RNC service areas. 

WCDMA mobility management procedures such as the “Cell/ Universal Mobile Telecommunications 

System Terrestrial Radio Access Network Registration Area (URA) Update and RNC Relocation 

procedure” are needed to reflect these aircraft movement scenarios. 

In Scenario IV, an aircraft moves across the SGSN area and needs to update from an old RNC and an 

old SGSN to a new RNC and a new SGSN service area. The network requires a mechanism to request 

location updates when a new SGSN service area is entered. Figure 35 shows a sequence diagram that 

reflects the Scenario IV cell update and RNC relocation mechanism. 

3.6.3 Other Selected Data Link Services 

The remainder of the data link service mappings can be found in appendix B. 
NASA/CR—2008-214987 32

3.7 Conclusions 

Applying the WCDMA standards as defined, the study indicates that a full complement of WCDMA 

functional elements is required to provision COCR services. Not only the air interface and elements of the 

radio network controller are needed, but also elements of the core network such as HLR, SGSN, and 

GGSN. Required implementation of a full complement of WCDMA functionally elements and protocols 

affects cost, certification, and standardization because of the anticipated correlations between number of 

ground elements and cost, required number of functional elements and complexity and/or risk of 

certification, and number of ground/protocol elements and standardization complexity and/or risk. 
NASA/CR—2008-214987 33

4.0 P34/TIA–902 Intellectual Property Assessment 

Phases I and II of the FCS recommended a set of technologies for further consideration for 

applicability to the FRS. This included P34, a set of public safety radio system standards. Because there 

are some patents associated with the P34/TIA–902 standards, it is informative to evaluate the potential 

impact of its intellectual property rights in the context of an FRS implementation. This topic is addressed 

in the following subsections. 

4.1 Introduction to Intellectual Property 

According to United States Patent and Trademark Office (USPTO)3 (footnote 14): 

A U.S. patent for an invention is the grant of a property right to the inventor, issued by the 

United States Patent and Trademark Office. Generally, the term of a new patent is 20 years from 

the date on which the application for the patent was filed in the United States. 

The right conferred by the patent grant is, in the language of the statute and of the grant itself, 

“the right to exclude others from making, using, offering for sale, or selling” the invention in the 

United States or “importing” the invention into the United States. What is granted is not the right to 

make, use, offer for sale, sell or import, but the right to exclude others from making, using, offering 

for sale, selling or importing the invention. Once a patent is issued, the patentee must enforce the 

patent without aid of the USPTO. 

4.2 Introduction to P34/TIA–902 Standards 

 APCO (Association of Public-Safety Communications Officers) Project 34 (P34) is an 

Electronics Industries Alliance/TIA standardized public safety radio system. The P34/TIA–02 

concept was defined through a government and commercial partnership in order to provide 

universal access to all subscribers through a carefully controlled managed network. P34/TIA–

902 addresses “issues that restrict the use of commercial services for mission critical public 

safety wireless applications” such as Priority Access and System Restoration, Reliability, 

Ubiquitous Coverage, and Security. P34/TIA–902 specifications are documented in the APCO 

Standards; they were developed by TR–8 Private Radio Technical Standards Committee under 

sponsorship of the TIA in accord with a memorandum of understanding between TIA and 

APCO/National Association of State Telecommunications Directors (NASTD)/FED. 

P34/TIA–902 is considered a wideband public safety digital radio system that provides high-speed 

packet data services using the internet protocol (IP) on 50-, 100-, and 150-kHz channels and is designed 

for implementation in the 700 MHz band. The P34/TIA–902 system is defined with open, standardized 

interfaces so that manufacturers’ equipment can be interoperable. It is the intent of the P34/TIA–902 

specification that a system may be implemented where the equipment on either side of any open interface 

may be supplied by any manufacturer. The three open interfaces that are defined are the Wideband Air 

Interface (UW); Data Peripheral Interface (Mobile Data Peripheral to Mobile Radio Control, AW); and 

Data Interface (Radio Frequency Gateway to Data End System, EW). The defined functional groups 

include the mobile radio, mobile routing and control, mobile data peripheral, base radio, base routing, and 

control and radio frequency gateway. P34/TIA–902 systems can provide connectivity between mobile 

radios and fixed network equipment (FNE); mobile radios to repeaters to mobile radios; and direct radioto-radio (either mobile or fixed) connectivity. A depiction of the P34/TIA–902 open system architecture 

is shown in figure 36. 

 

3

Information is from USPTO Web site, http://www.uspto.gov/. 
NASA/CR—2008-214987 34

The P34/TIA–902 protocol stack is layered, and assumes a point of attachment to an IP network. The 

P34/TIA–902 system is specified to provide IP version 4 (IPv4) and IPv6 bearer services for the transport 

of packet data using the IP suite of protocols. The wideband IPv4 (and IPv6) delivery service is required 

to directly support standard IP transport layers, including user datagram protocol (UDP), transmission 

control protocol (TCP) and real time protocol (RTP). This is shown in figure 37. 

4.2.1 Patents in P34/TIA–902 Standards 

There are eight patents associated with P34/TIA–902 standards, two of which are associated with 

Media Access Control/Radio Link Adaptation (MAC/RLA) layer specifications; six are in the physical 

(PHY) layer (Scalable Adaptive Modulation (SAM), channel coding (CHC), or IOTA). Table III lists 

these patents with patent name, patent number and date, patent assignee, associated P34/TIA–902 

specification and protocol layer. 
NASA/CR—2008-214987 35

TABLE III.—PATENTS IN P34/TIA–902 STANDARDS 

No. Patent name Patent 

number 

Patent assignee P34/TIA–902 specification Protocol 

layer 

1 Encryption Synchronization 

with Encryption Key 

Identification 

US 5,185,796 

Feb. 9, 1993 

Motorola, Inc. TIA–902.BAAC 

Wideband Air Interface 

MAC/RLA Layer 

Specification, Sept. 2002 

MAC/RLA 

2 Power Amplifier Linearization 

in a TDMA Mobile Radio 

System 

US 5,559,807 

Sept. 24, 1996 

Motorola, Inc. TIA–902.BAAC 

Wideband Air Interface 

MAC/RLA Layer 

Specification, Sept. 2002 

MAC/RLA 

3 Method for Providing and 

Selecting Amongst Multiple 

Data Rates in a Time Division 

Multiplexed System 

US 5,533,004 Motorola, Inc. TIA–902.BAAD–A 

Scalable Adaptive Modulation 

(SAM) Channel Coding 

Specification, Sept. 2003 

SAM CHC 

4 Communication Signal Having 

a Time Domain Pilot 

Component 

US 5,519,730 

May 21, 1996 

Jasper TIA–902.BAAB–A 

SAM Physical Layer 

Specification, Sept. 2003 

TIA–902.BBAB 

SAM & 

IOTA PHY 

5 Peak to Average Power Ratio 

Reduction Methodology for 

QAM Communications 

Systems 

US 5,381,449 

Jan. 10, 1995 

Motorola, Inc. TIA–902.BAAB–A 

SAM Physical Layer 

Specification, Sept. 2003 

SAM PHY 

6 Quadrature Amplitude 

Modulation Synchronization 

Method 

US 5,343,499 

Aug. 30, 1994 

Motorola, Inc. TIA–902.BAAB–A 

SAM Physical Layer 

Specification, Sept. 2003 

SAM PHY 

7 Scalable Pattern Methodology 

for Multicarrier 

Communication Systems 

US 6,424,678 

Jul. 23, 2002 

Motorola, Inc. TIA–902.BAAB–A 

SAM Physical Layer 

Specification, Sept. 2003 

SAM PHY 

8 Construction of a Multicarrier 

Signal 

US 6,278,686 France 

Telecom and 

Télédiffusion 

de France 

TIA–902.BBAB 

Wideband Air Interface 

Isotropic Orthogonal 

Transform Algorithm Physical 

Layer Specification 

IOTA PHY 

4.3 Assessment Approach 

As shown in figure 38, a six-step approach assessed P34/TIA–902 intellectual property. The first step 

is to identify patents listed in the P34/TIA–902 specifications; step 2 is to order these patents (textual 

technical descriptions) from the USPTO; in step 3, each of these patents were studied carefully and a 

high-level summary of each patent is presented for steps 4 and 5 reviews. In step 4, a corporate-level 

patent counsel was invited to review issues; meanwhile, impacts of patents to potential P34/TIA–902 

application to FRS were addressed. In step 5, a team review was conducted to obtain inputs from different 

technical perspectives. Steps 4 and 5 were iterated until a consensus was achieved. Finally in step 6, 

recommendations for each patent were proposed and documented. 
NASA/CR—2008-214987 36

4.3.1 Propose a Recommendation 

For this study, recommendations specific to reviewed patents took the form of three implementation 

options, including 

1. Bypass the Patent: This is the case when the patented features are not desirable applications and 

are considered to not be part of an FRS solution. 

2. Find an Alternative Solution: In this case, the patented features are considered desirable, but 

could be implemented in a different manner; or only a subset of the functionality described in the 

patent is considered for implementation. 

3. Implement the Patent: This is the case the identified patented feature is desirable, and there 

appears to be no alternative solution; thus, full implementation of the patent is expected. 

Proposed recommendations were determined based on the desirability and criticality of the patents. 

• Desirability: Are the claimed benefits desirable in FRS? 

• Criticality: Can P34/TIA–902 be implemented without this patent? Will overall P34/TIA–902 

performance be affected when the patent is not implemented? Is there an alternative solution? 

4.3.2 Terms and Assumptions 

In the process of proposing recommendations for the patents, certain terms and assumptions were 

found to be applicable. They are 

1. All eight patents will all expire prior to FCS equipment deployment (assuming 2020 rollout). The 

term of a new patent is 20 years from the date on which the application for the patent was filed in 

the United States and is not renewable. 

2. U.S. patents are not applicable to companies outside the United States. U.S. patents are not 

effective to implementations outside United States. 

3. P34/TIA–902 physical layer modifications have been identified as needed for the application of 

this technology in the L-band aeronautical channel; six out of eight patents address features of the 

physical layer. 

4. P34/TIA–902 has more flexibility than FRS applications may need; sometimes only a subset of 

the P34/TIA–902 characteristics is needed. Partial implementation of a patent is considered a 

“Alternative Solution” case (as the patent would not be applicable). 
NASA/CR—2008-214987 37

5. FRS ground infrastructure will likely be optimized for one modulation type, not for multiple 

modulation types, this reflects feedback received in FCS Phase I interim results in which the 

P34/TIA–902 concept of use included multiple modulation features was noted to adding 

unnecessary complexity and is not desirable. 

6. Current analysis results suggest that quadrature phase skift-keying (QPSK) is likely sufficient to 

meet COCR requirements (quadrature amplitude modification (QAM) is not likely to be 

necessary). 

4.4 Patent Assessments 

Assessment results of the P34/TIA–902 associated patents are listed in this section. For each patent, 

the assessment result is given in the following form 

• Name, number, assignee, and date 

• Abstract of the patent 

• Impact (assessment questions and answers regarding desirability and criticality of the patents) 

• Proposed recommendation 

Detailed descriptions of the patents are not available in this document, but can be requested from 

USPTO at http://www.uspto.gov/. 

4.4.1 Patent 1 

Name, number, assignee 

Encryption Synchronization Combined with Encryption Key Identification 

US 5,185,796, February 9, 1993, Motorola 

Abstract of the patent 

This patent describes a methodology to support the use of multiple encryption algorithms and/or 

encryption keys at MAC/RLA layer in a radio communication system. 

Impact 

Question Answer 

Are the claimed benefits desirable in FRS? In COCR security requirements, cryptographic protection 

is identified as a preferred approach to mitigate three of 

the identified threats, and it states that this protection can 

be at the link layer, network layer, or application layer. 

This capability may be needed. 

Can P34/TIA–902 be implemented without this patent? Yes, when not use link layer encryption 

Will overall P34/TIA–902 performance be affected when 

the patent is not implemented? 

No, just drives higher layer requirements 

Is there an alternative solution? Possible, but not desirable for FRS 

Recommendation: Bypass 

4.4.2 Patent 2 

Name, number, assignee 

Power Amplifier Linearization in a TDMA Mobile Radio System 

US 5,559,807, September 24, 1996, Motorola 
NASA/CR—2008-214987 38

Abstract of the patent 

This patent describes a methodology for using predetermined linearization time slots in a TDMA 

radio system to transmit training signals so that receiver can linearize its power amplifier during that 

time slot. This approach avoids the use of substantial additional hardware and uses a minimum time 

allocated for training sequence and therefore causes minimum transmission delay. 

Impact 

Question Answer 

Are the claimed benefits desirable in FRS? Yes 

Can P34/TIA–902 be implemented without this patent? No (requires framing structure change—not an 

insignificant change) 

Will overall P34/TIA–902 performance be affected when the 

patent is not implemented? 

Yes, functionally can be bypassed with re-work of MAC 

layer, but less capacity for data 

Is there an alternative solution? Probably yes, but it does require substantive changes 

to the frame structure in MAC layer 

Recommendation: Implementation of the patent is desirable

4.4.3 Patent 3 

Name, number, assignee 

Method for Providing and Selecting Amongst Multiple Data Rates in a Time Division Multiplexed 

System 

US 5,533,004, July 2, 1996, Motorola 

Abstract of the patent 

This patent defines an approach to TDMA that supports dynamic change in modulation to adjust to 

signal conditions. The approach combines multiple coding schemes with multiple modulation 

constellations that optimize TDMA time slot utilization resulting in maximum data throughput given 

channel conditions. 

Impact 

Question Answer 

Are the claimed benefits desirable in FRS? Yes 

Can P34/TIA–902 be implemented without this patent? No (requires framing structure change—not an 

insignificant change) 

Will overall P34/TIA–902 performance be affected when the 

patent is not implemented? 

Yes, functionally can be bypassed with re-work of MAC 

layer, but less capacity for data 

Is there an alternative solution? Probably yes, but it does require substantive changes 

to the frame structure in MAC layer 

Recommendation: Alternative Solution

4.4.4 Patent 4 

Name, number, assignee 

Communication Signal Having a Time Domain Pilot Component 

US 5,519,730, May 21, 1996, Individual Inventors 

Abstract of the patent 

This patent describes a methodology for using time domain pilot symbols in a multicarrier communication 

system that allows for proper demodulation of information signals. Specific patent claims describe signal 

demodulation using pilot symbols that includes both phase and amplitude corrections. 
NASA/CR—2008-214987 39

Impact 

Question Answer 

Are the claimed benefits desirable in FRS? No, if use QPSK modulation 

Can P34/TIA–902 be implemented without this patent? Yes, if QPSK is the only modulation type used 

Will overall P34/TIA–902 performance be affected when the 

patent is not implemented? 

No, if QPSK is the only modulation type used 

Is there an alternative solution? Yes, other OFDM demodulation techniques should be 

evaluated if redesign P34/TIA–902 physical layer 

Recommendation: Bypass

4.4.5 Patent 5 

Name, number, assignee 

Peak to Average Power Ratio Reduction Methodology for QAM Communication Systems 

US 5,381,449, January 10, 1995, Motorola 

Abstract of the patent 

This patent describes a methodology to reduce peak to average power ratio by preselecting pilot 

amplitudes and phases for multiple subchannel, N-level QAM communication system 

Impact 

Question Answer 

Are the claimed benefits desirable in FRS? No, if use QPSK modulation 

Can P34/TIA–902 be implemented without this patent? Yes, if QPSK is the only modulation type used 

Will overall P34/TIA–902 performance be affected when the 

patent is not implemented? 

No, if QPSK is the only modulation type used 

Is there an alternative solution? Possible, need further analysis, but not desirable for 

FRS 

Recommendation: Bypass

4.4.6 Patent 6 

Name, number, assignee 

Quadrature Amplitude Modulation Synchronization Method 

US 5,343,499, August 30, 1994, Motorola 

Abstract of the patent 

This patent describes a methodology for generating a synchronization sequence for a QAM 

communication system that reduces computational complexity required for data reception 

Impact 

Question Answer 

Are the claimed benefits desirable in FRS? No, if use QPSK modulation 

(Yes, if use QAM and want to simplify receiver) 

Can P34/TIA–902 be implemented without this patent? Yes, if use QPSK modulation 

Will overall P34/TIA–902 performance be affected when the No for QPSK modulation 

patent is not implemented? Yes for QAM. Potential receiver cost may go up as 

receiver needs higher computational complexity 

Is there an alternative solution? Possible, need further investigation, but not desirable 

for FRS 

Recommendation: Bypass 
NASA/CR—2008-214987 40

4.4.7 Patent 7 

Name, number, assignee 

Scalable Pattern Methodology for Multi-Carrier Communication Systems 

US 6,424,678, July 23, 2002, Motorola 

Abstract of the patent 

This patent describes a methodology for scaling a base pattern of pilot symbols for various numbers 

of subchannels in a multicarrier communication system. 

Impact 

Question Answer 

Are the claimed benefits desirable in FRS? No, no benefit in defining a scalable base pattern for a 

specific number of subchannels. FRS will pick one 

bandwidth instead if multiple subchannels and will 

optimize pilot pattern for that case 

Can P34/TIA–902 be implemented without this patent? Yes, a new symbol mapping figure will be required 

Will overall P34/TIA–902 performance be affected when the 

patent is not implemented? 

No, a new pattern can be defined and work as well 

Is there an alternative solution? Possible, need further investigation 

Recommendation: Bypass 

4.4.8 Patent 8 

Name, number, assignee 

Construction of a Multicarrier Signal 

US 6,278,686, France Telecom & Télédiffusion De France, August 21, 2001 

Abstract of the patent 

This patent describes a methodology for creating a multicarrier communication signal by undergoing 

spectral processing to compress the signal in the time domain. 

Impact 

Question Answer 

Are the claimed benefits desirable in FRS? Possible only if pulse transmission is desired 

Can P34/TIA–902 be implemented without this patent? No, but need to be validated with further research 

Will overall P34/TIA–902 performance be affected when the 

patent is not implemented? 

Yes, if use IOTA physical layer 

Is there an alternative solution? Unknown at this time 

Recommendation: Bypass 

4.5 Conclusions 

From the analysis results shown in table IV, the following conclusions can be drawn: 

• The concept of use defined for P34/TIA–902 makes some patents not applicable (for example, 

IOTA physical layer not used in the FCS application and associated patents do not apply); also 

recommended tailoring of physical layer standard for the FCS application results in bypassing of 

most physical layer patents. 

• Only one patent is assessed as desirable to implement, it is a methodology proposed for power 

amplifier linearization, modification of which would influence MAC framing structure. 
NASA/CR—2008-214987 41

• Most if not all patents will expire before timeframe of FCS. 

• These patents are not applicable to companies outside United States. 

• Intellectual property associated with P34/TIA–902 standard is deemed to have little or no impact 

on the FRS if it is an implementation based on this standard. 

TABLE IV.—PATENT EVALUATION SUMMARY 

No. Patent name Patent number Protocol layer Decision Comment 

1 Encryption Synchronization 

Combined with Encryption 

Key Identification 

US 5,185,796 

Feb. 1993 

Motorola 

Filed May 1991 

MAC/RLA Bypass Implementation could be achieved 

by driving requirements to upper 

layers 

2 Power Amplifier 

Linearization in a TDMA 

Mobile Radio System 

US 5,559,807 

Sept. 1996 

Motorola 

Filed 1994 

MAC/RLA Implement 

patent 

desirable 

(expires 

2014) 

Alternative implementation could 

be achieved, but requires 

modification to MAC layer 

3 Method for Providing and 

Selecting Amongst Multiple 

Data Rates in a Time 

Division Multiplexed 

System 

US 5,533,004 

Jul. 1996 

Motorola 

Filed 1994 

SAM Channel 

Coding 

Alternative 

solution 

Adaptive data rate not a desirable 

feature 

4 Communication Signal 

Having a Time Domain 

Pilot Component 

US 5,519,739 

May 1996 

Jasper 

Filed 1991 

SAM & IOTA 

PHY 

Bypass Develop new PHY 

5 Peak to Average Power 

Ratio Reduction 

Methodology for QAM 

Communications Systems 

US 5,381,449 

Jan. 1995 

Motorola 

Filed 1991 

SAM PHY Bypass Develop new PHY, and QAM is not 

identified modulation in CONUSE 

6 Quadrature Amplitude 

Modulation 

Synchronization Method 

US 5,343,499 

Aug. 1994 

Motorola 

SAM PHY Bypass Develop new PHY, and QAM is not 

identified modulation in CONUSE 

7 Scalable Patter 

Methodology for 

Multicarrier 

Communication Systems 

US 6,424,678 

Jul. 2002 

Motorola 

Filed 2000 

SAM PHY Bypass Develop new PHY 

8 Construction of a 

Multicarrier Signal 

US 6,278,686 

Aug. 2001 

France Telecom & 

Télédiffusion De 

France 

Filed 1996 

IOTA PHY Bypass Develop new PHY 
NASA/CR—2008-214987 42

5.0 Summary of Results 

This report documents the indepth studies that have been carried out during the third phase of the FCS 

technology investigation task. The studies included L-Band Interference Measurements; WCDMA 

Functional Assessment; and P34/TIA–902 Intellectual Property Assessment. A summary of results 

specific to each study are noted below. 

L-Band Interference Measurements: 

• The power levels expected from continuously transmitting FRS equipment onboard the aircraft 

may be sufficiently high as to cause desensitization in the DME interrogator. This phenomenon 

was evident for all of the FRS candidates even at large frequency separations for the DME that 

was tested. This finding is not favorable for FRS candidate technologies whose concept of use 

assumes continuous transmissions (e.g., WCDMA). 

• The data also indicates that the DME interrogator is more tolerant to gated transmissions (i.e., 

there is potential for implementation of a technology with a gated waveform; but off-set channels 

may still be required (to be investigated)). A majority of the measurements used 100 percent duty 

cycles, which results in a conservative analysis. Lesser duty cycles may be expected in practice. It 

is expected that low-to-moderate duty cycles will interfere less with DME compared to FRSs with 

high duty cycles. This finding may be favorable for FRS candidate technologies whose concept of 

use assumes noncontinuous transmissions (i.e., LDL and P34/TIA–902 (partial)). 

• It is recommended that further analysis be conducted to characterize the relationship between 

FRS duty-cycle and interference susceptibility (the duty-cycle investigation should include more 

variables than just overall duty cycle; there may be some combination of specific timescales of 

on/off pulses and overall duty cycle that results a seemingly “invisible” waveform from the DME 

interrogator’s perspective); in the context of this investigation, identification of collocation 

constraints can also be investigated. It is also recommended that different models of DME 

interrogators be tested to provide a range of performance. 

WCDMA Functional Assessment: 

• Applying the WCDMA standards as defined, the study indicates that a full complement of 

WCDMA functional elements is required to provision COCR services. Not only the air interface 

and elements of the radio network controller are needed, but also elements of the core network 

such as HLR, SGSN, and GGSN. Required implementation of a full complement of WCDMA 

functionally elements and protocols has impact on cost, certification, and standardization because 

of the anticipated correlations between number of ground elements and cost, required number of 

functional elements and complexity and/or risk of certification, and number of ground/protocol 

elements and standardization complexity and/or risk. 

P34/TIA–902 Intellectual Property Assessment: 

• The concept of use defined for P34/TIA–902 makes some patents not applicable (e.g., IOTA 

physical layer not used in the FCS application and associated patents do not apply); also 

recommended tailoring of physical layer standard for the FCS application results in bypassing of 

most physical layer patents. 

• Only one patent is assessed as desirable to implement, it is a methodology proposed for power 

amplifier linearization, modification of which would influence MAC framing structure. 

• Most if not all patents will expire before timeframe of FCS. 
NASA/CR—2008-214987 43

• These patents are not applicable to companies outside the United States. 

• Intellectual property associated with P34/TIA–902 standard is deemed to have little or no impact 

on the FRS if it is an implementation based on this standard. 

The results of the studies noted above will be used to support the final technology evaluation and 

technology recommendation development effort, the last component of the FCS technology investigation 

study. The final FCS technology investigation report, to be published in early 2008, will document the 

overall technology evaluation results and subsequent recommendations. 

NASA/CR—2008-214987 45

Appendix A—Unfiltered Interference Measurement Results 

The measurements results continued in this appendix are the unfiltered measurement results that were 

collected during the first pass of the measurement campaign. The filtered measurements can be found in 

Section 2. Figures 39, 40, and 41 show the interference measurements. 
NASA/CR—2008-214987 46
NASA/CR—2008-214987 47

NASA/CR—2008-214987 49

Appendix B—Additional WCDMA Functional Analysis Results 

This appendix provides additional WCDMA functional analysis result as described in Section 3. 

B.1 ACM (ATC Communication) Service 

CPDLC (controller pilot data link communication) is a means of communication between controller 

and pilot, using data link for ATC communications. 

• CPDLC allows two-way communications between pilot and controller, but using data link rather 

than voice. It is especially useful in areas where difficult-to-use high-frequency (HF) 

radiotelephony was previously used for communication with aircraft, for example. oceans. 

The data link service for ATC is enabled through the use of CPDLC, ACM is used to 

• Establish CPDLC with an ATSU 

• Terminate CPDLC with an ATSU 

• Transfer voice comm and CPDLC form the T-sector/T-ATSU to the R-sector/R-ATSU 

• Issue a change of frequency when this happens: 

– Initiated by the T-sector/T-ATSU, or 

– A request from the R-sector/R-ATSU, or 

– A request from the flight crew 

Possible operating methods for ACM service are 

• Transfer from T-ATSU to R-ATSU, both using CPDLC 

• Transfer from T-ATSU not using CPDLC to R-ATSU using CPDLC 

• Transfer from T-ATSU using CPDLC to R-ATSU not using CPDLC 

• Transfer and/or change of frequency with no change in the established CPDLC, both sectors 

using CPDLC 

• Transfer from T-sector not using CPDLC to R-sector using CPDLC, with no change in the 

established CPDLC 

• Transfer from T-sector using CPDLC to R-sector not using CPDLC, with no change in the 

established CPDLC 

• Termination of CPLDC without transfer of CPDLC or change of frequency 

Three ACM functions exchanged between a moving aircraft and multiple ATSUs are illustrated in 

figure 42. 

Two ACM Service Mapping Scenarios

• Mapping Scenario 1 

– ACM service operating method (a) 

ο Transfer from T-ATSU to R-ATSU, both using CPDLC 

– Network Domain (II) 

ο Same RNC routing area and same RNC region 

• Mapping Scenario 2 

– ACM service operating method (a) 

ο Transfer from T-ATSU to R-ATSU, both using CPDLC 

– Network Domain (IV) 

ο Different RNC routing area and different SGSN region 
NASA/CR—2008-214987 50

A routing area update should take place when a WCDMA UE (aircraft) detects that it has entered a 

new routing area. 

Mapping of scenario 1 and scenario 2 to WCDMA functions are shown in figures 43, 44, and 45. 
NASA/CR—2008-214987 51

B.2 ATC Clearance (ACL) Service 

ACL service supports operational communication between the flight crew and the controller of 

the Current Data Authority ATSU. ACL service is preceded by ACM Service, operating methods are 

• Request clearances 
NASA/CR—2008-214987 52

• Issue and expect clearances 

• Issue requests for current or future flight status 

• Provide advisory information such as meteorological or operational conditions 

• Provide flight status notifications 

The operational context of ACL service is shown in figure 46. ACL functions exchanged between a 

moving aircraft ATSU are illustrated in figure 47. Mapping of ACL Clearance function into WCDMA 

service is shown in figure 48. 
NASA/CR—2008-214987 53

B.3 AMC (ATC Microphone Check) Service 

The AMC service provides controllers with the capability to uplink an instruction to an aircraft in 

order for the flight crew to check that the aircraft is not blocking a given voice channel. The AMC 

operational context and time sequence is shown in figure 49. Mapping of AMC service to WCDMA 

functions is shown in figure 50. 

B.4 Departure Clearance (DCL) Service 

DCL provides automated assistance for requesting and delivering clearances, when DCL is provided 

through the use of CPDLC, this information can be exchanged using CPDLC message elements. DCL 

service is intended for use during the surface phase of operation. The DCL operational context and time 

sequence is shown in figure 51. Mapping of initial DCL service to WCDMA functions is shown in 

figure 52. DCL clearance revision in WCDMA context is shown in figure 53. 
NASA/CR—2008-214987 54

B.5 Downstream Clearance (DSC) Service 

The DSC service is needed when flight crews need to obtain clearances or information from ATSUs 

that will be responsible for control of the aircraft in the future. Only flight crew can initiate the DSC 

service with a D-ATSU. The DSC operational context and time sequence is shown in figure 54. Mapping 

of DSC service to WCDMA functions is shown in figure 55. 
NASA/CR—2008-214987 55
NASA/CR—2008-214987 56

B.6 D-ATIS (Data Link Automatic Terminal Information Service) 

Automatic Terminal Information Service (ATIS) is a continuous broadcast of recorded noncontrol 

information in busier terminal areas. ATIS broadcasts contain essential information, such as weather 

information, which runways are active, available approaches, and any other information required by the 

pilots, such as notices to airmen (NOTAMs). Pilots usually listen to an available ATIS broadcast before 

contacting the local control tower, in order to reduce the controllers’ workload and relieve frequency 

congestion. The D-ATIS automatically generates ATIS information and also provides the ability to send 

the same information to the pilots using digital texts. This service is installed to reduce workload on the 

air traffic controllers as well as reduce the chances of misunderstandings. 
NASA/CR—2008-214987 57

Two modes: 

• Demand mode—a single ATIS report requested, or 

• Contract mode—an ATIS report followed by updates when they occur 

The DCL operational context is shown in figure 56. D-ATIS demand and contract mode time 

sequence is shown in figure 57. D-ATIS function in WCDMA context is shown in figure 58. 

B.7 FLIPCY (Flight Plan Consistency) Service 

FLIPCY is used to automatically detect inconsistencies between the ATC flight plan and the flight 

plan activated in the aircraft system. It provides controllers with automated support confirming that the en 

route and terminal area portions of the aircraft system and ATSU flight plans conform. If an inconsistency 

is detected, the controller is informed. 

The service may be initiated 

• Before the aircraft takeoff and/or 

• A parameter amount of time before entering the ATSU area of responsibility and/or 

• At the time of entry into the ATSU’s area of responsibility and/or 

• At controller’s discretion 

FLIPCY requires that DLIC be performed to determine the aircraft’s capability to accomplish the 

service. 

The FLIPCY operational context and time sequence is shown in figures 59 and 60. Mapping of 

FLIPCY service to WCDMA functions is shown in figure 61. 
NASA/CR—2008-214987 58
NASA/CR—2008-214987 59
NASA/CR—2008-214987 60
NASA/CR—2008-214987 61

Appendix C—Summary of Previous Indepth Assessments 

Many of indepth technical assessments supporting the FCS technology assessment were performed 

during the FCS Phase II summary. An overview of the work performed and results is provided in the 

following subsections: 

• Section C.1: L-Band Air/Ground (A/G) Channel Characterization 

• Section C.2: P34/TIA–902 Performance Assessment 

• Section C.3: LDL Performance Assessment 

• Section C.4: L-Band Technology Cost Assessment for Ground Infrastructure 

• Section C.5: L-Band Interference Analysis 

• Section C.6: Satellite Technology Availability Performance 

• Section C.7: C-Band Technology (Institute of Electrical and Electronics Engineering (IEEE) 

802.16e) Performance 

C.1 L-Band Air/Ground (A/G) Channel Characterization 

To support the assessment of technology performance in the L-Band Air-Ground (A/G) channel, a 

literature search revealed that while many channel models exist for the terrestrial channel in close 

proximity to L-band, there had been no previous activity to develop a channel model that characterizes 

the L-band A/G channel for radio communications. As most standardization bodies consider it a best 

practice to test candidate waveform designs against carefully crafted channel models that are 

representative of the intended user environment, a channel model was developed that could be used for 

common characterization of communications waveform performance in this A/G channel. 

Characterization of the delay spread and the Doppler Power Spectrum is essential for generating a 

useful model for waveform simulation and evaluation of candidate FRS technologies in L-band. In order 

to form estimates of the delay spread and associated statistics, a ray-tracing simulation was developed. 

This simulation models both diffuse and specular reflections from the Earth’s surface. The developed 

simulation used a method of concentric oblate spheroids to model multipath contributions. The desired 

product was the set of points on the terrain that were intersected by the oblate spheroids. When plotted, 

each set of intersection points appears as a distorted annulus approximating the cross section of the 

spheroid when sliced by the Earth’s surface. Each set of intersection points is mutually exclusive from 

any other set because any intersection point can only be accounted for once. Each set of intersection 

points contributes to multipath for a particular delay. Figure 62 illustrates the method of concentric oblate 

spheroids used to model multipath contributions. 

Implementing the methodology to apply ray tracing to determine specific specular and diffuse 

multipath components and employing data reduction and analysis techniques, the root mean square 

(RMS) delay spread was calculated to be 1.4 μs. It is instructive to consider representative technologies at 

this point since the technology data rate will drive channel model parameter estimation. A rule of thumb 

frequently applied is that if the mean RMS delay spread is at least one-tenth of the symbol duration, then 

the channel is frequency-selective. In order to illustrate this, two technologies emerging from the FCS 

Phase I study were considered: LDL and P34/TIA–902. Table V shows the corresponding data rates and 

symbol durations for LDL and P34/TIA–902. 

TABLE V.—DATA RATES OF LDL AND P34/TIA–902 

Data rate, kbps Symbol duration, μs 1/10 of the symbol duration, μs 

Waveform R 

R

Tb

1 = t0 = Tb /10

LDL 62.5 16.0 1.60 

P34/TIA–902 4.8a 208.3 20.83 a

P34/TIA–902 is an OFDM system. The tabulated data rate is per carrier and is the symbol rate. Overall 

P34/TIA–902 data rates range from 76.8 to 691.2 kbps. 
NASA/CR—2008-214987 62

 

Using our vision, P34/TIA–902 should undergo flat fading and LDL presents a borderline case 

because the mean RMS delay spread is very close to one-tenth of the symbol duration. It is important to 

note that frequency-selective channel models differ in structure from flat fading channel models. For this 

reason it was decided to develop a frequency-nonselective fading model for P34/TIA–902 and a 

frequency-selective fading model for LDL. 

First the channel model for LDL is described. Figure 63 shows the block diagram representation for a 

deterministic simulation model for a frequency-selective mobile radio channel (Pätzold 270). 

The parameters that define the LDL channel model are as follows: 

• Number of taps (N) 

• Tap spacing (a0, a1, ..., aN) 

• Tap weights (D1, D2, ..., DN) 

• Tap fading processes (μ0, μ1, ..., μN) 

Table VI defines the LDL channel model parameters that were derived in the Phase II study. 

TABLE VI.—LDL CHANNEL MODEL PARAMETERSa

Tap no. Delay, 

μs 

Power, 

linear 

Power, 

dB 

Fading process Doppler category 

1 0.0 1.0000 0 Ricean Jakes 

2 1.6 0.0359 –14.5 Rayleigh Jakes 

3 3.2 0.0451 –13.5 Rayleigh Jakes 

4 4.8 0.0689 –11.6 Rayleigh Jakes 

5 6.4 0.0815 –10.9 Rayleigh Jakes 

6 8.0 0.0594 –12.2 Rayleigh Jakes 

7 9.6 0.0766 –11.2 Rayleigh Jakes a

Note that the assumptions used in the development of the Jakes model are not applicable for the anticipated Ricean 

A/G channel, but this model has been incorporated to provide a conservative estimate of Doppler effects. 

The P34/TIA–902 channel model is much less complex than the LDL channel model because the 

channel is frequency-nonselective. Figure 64 illustrates the P34/TIA–902 channel model. 
NASA/CR—2008-214987 63

The Ricean fading process is derived in the complex baseband by creating two colored Gaussian 

processes. The Rice method is used to generate the gaussian processes as a summation of sinusoids whose 

coefficients and frequencies are determined by the Doppler Power Spectrum of the channel. As the 

process is Ricean, a time-variant mean is summed with the colored gaussian process (loss of signal (LOS) 

component). The magnitude of the complex gaussian colored processes yields the Ricean process with 

fade durations and amplitudes determined by the channel. 

One of the primary results reported is the simulated RMS delay spread. It should be noted that this 

delay spread can be modeled as a function of the average distance from the transmitter, with increasing 

delay spreads reported for increasing distances. Because of this phenomenon, our simulated positions 

were constrained to be in an area with dimensions that were small compared to the average distance from 

the transmitter. For these simulations, an RMS delay spread of 1.4 μs was predicted for a certain distance 

(average distance = 40 miles) from the transmitter in mountainous terrain. A generalized model, using the 

method cited in Greenstein, has the form 

στ = στ d ε A 0

where 

d is the distance in km 

σ0 is the median value of the RMS delay spread at d = 1 km 

ε is an exponent that lies between 0.5 and 1.0, based on the terrain type 

A is a lognormal variate 

To determine the parameters that are appropriate for a generalized L-band A/G model in mountainous 

terrain, RMS delay spreads were predicted for a reference distance of 1 km as well as for the previously 

mentioned values at 64.37 km (40 miles). The two predicted values that resulted from the simulation work 

are 

σRMS(1 km) = 0.1 μs 

σRMS(64.37 km) = 1.4 μs 

Fitting the Greenstein model to the reference data provides a generalized expression for RMS delay 

spread, which is found to be 

0.1 s ( 6 ) 0.6337 στ = × d μ A = dB

A full description of the L-band A/G channel characterization work is provided in the interim FCS 

Phase II report, Section E.1. 
NASA/CR—2008-214987 64

C.2 P34/TIA–902 Performance Assessment 

In addition to L-band channel characterization, L-band technology performance studies specific to 

individual technologies were also conducted. An indepth analysis of P34/TIA–902 net entry, data transfer, 

and bit error rate (BER) performance in the L-band channel was performed. The simulation of P34/TIA–

902 included evaluation of a ground station and 95 mobile nodes (COCR-defined NAS super sector) 

employing P34/TIA–902 SAM physical layer properties associated with 50-kHz channelization and 

QPSK modulation. Simulation model results are shown in figure 65. These figures show the response 

time of the P34/TIA–902 simulation to the offered load for each of transmitted message. Note that the 

subnetwork latencies over P34/TIA–902 protocols (subnetwork dependent control protocol (SNDCP), 

LLC CP, LLC UP, and MAC) meet COCR latency requirements. Specifically, although there are some 

startup outliers, 95 percent of delay measurements are under 0.7 s. Reference the interim FCS Phase II 

report, Section E.1.2.2. 

In addition to simulation of P34/TIA–902 net entry and data transfer performance, P34/TIA–902 

performance in the defined L-band A/G channel was also evaluated. As part of this effort, P34/TIA–902 

transmitter and receiver models were generated. Specifically, the P34/TIA–902 SAM physical layer 

interface was modeled by developing a custom application using C code. The transmitter was 

implemented as detailed in the specification for the 50-kHz channel using QPSK modulation. The 

receiver implementation was tested against published results for standardized channel models. 

Additionally, P34/TIA–902 coding gain (for specified concatenated Hamming codes) was investigated. It 

was found that a 3×10–3 raw BER is approximately equal to 10–5 coded BER for P34/TIA–902. 

The developed P34/TIA–902 transmitter and receiver models were combined with a model of the 

expected L-band channel based on analysis work previously described. Specifically, a two tap channel 

model was simulated where Tap 1 was modeled as Ricean, with a K-factor of 18 dB, unity gain, and Jakes 

Doppler Spectrum; and Tap 2 was modeled as Rayleigh, with a 4.8 μs delay, –18 dB average energy, and 

Jakes Doppler Spectrum (conservative estimate). In this model, the mobile velocity was taken to be 0.88 

mach. This is the maximum domestic airspeed given in the COCR based on Boeing 777 maximum speed. 

Additionally, in the model the P34/TIA–902 tuned frequency was taken to be 1024 MHz, with maximum 

Doppler shift of 1022 Hz. 

Initial simulations indicate good performance can be achieved in the aeronautical channel (e.g., flat 

channel effects), primarily a consequence of the strong line-of-sight component of the received signal 

(with K factors greater than 4). Figure 66 shows initial performance results and a complete description of 

the P34/TIA–902 performance assessment including simulation block diagrams, receiver implementation 

details (channel estimation using interpolation weighting), model validation results, and details on the 

simulation A/G channel are provided in Section E.1.2.3 of the interim FCS Phase II study report. 
NASA/CR—2008-214987 65

C.3 LDL Performance Assessment 

A second technology investigated for performance in the L-band aeronautical channel was LDL. As 

with P34/TIA–902, LDL transmitter and receiver models were generated and the receiver model validated 

against known results. After validation, investigation of LDL coding, Reed-Solomon (72, 62), provides a 

coding gain of 3 to 4 dB in the expected region of operation. LDL performance was simulated in the 

L-band aeronautical channel environment. The LDL channel model is a conservative model that 

introduces an irreducible error floor to system performance (reference Section C.1). The plot shown in 
NASA/CR—2008-214987 66

figure 67 shows the system performance of LDL in the presence of both additive white gaussian noise 

(AWGN) and the L-band aeronautical channel model. Based on the results of this simulation, LDL may 

require channel equalization to mitigate the effects of the A/G aeronautical channel model in L-band. 

A complete description of the LDL performance assessment including simulation block diagrams, 

receiver implementation details, model validation results, and details on the simulation A/G channel are 

provided in Section E.1.3.2 of the interim FCS Phase II study report. 

C.4 L-Band Technology Cost for Ground Infrastructure 

L-band technology cost was another focus area of indepth analysis. In this work, the economic 

feasibility from the perspective of the ground infrastructure provider was evaluated. This analysis was 

responsive to feedback received on the technology prescreening results (FCS Phase I) that indicated that 

due to cost constraints, an L-band solution is only considered should VHF spectrum prove insufficient to 

provide total required data link capability. The L-band business case analysis provided a first order of 

magnitude estimate of required investment for an L-band aeronautical ground infrastructure. The 

technical approach for accomplishing this objective included 

• Through detailed analysis, develop a notional ground L-band architecture that can meet Future 

Communication Infrastructure requirements as defined in the COCR document for ATC 

communications 

– Derive number of radio sites required for total U.S. coverage 

ο Perform L-band link budget analysis 

ß Develop L-band link budget spreadsheet and derive the parameters to close the link 

ß Excess path loss derivation 

ο Perform L-band coverage analysis 

ο Derive radio site redundancy to meet system availability requirements 

ο Develop an architecture to meet availability required 

• Determine if the business case can close 

– Develop cost elements and estimates for initial development and operations and maintenance 

– Determine required revenue flow to close the business case 

An overview of the technical approach workflow is shown in figure 68. 
NASA/CR—2008-214987 67

Details of the work performed to develop a link budget, determine radio site redundancy and defined 

the radio site equipment is provided in the interim FCS Phase II study report (Sections E.1.8.1 and 

E.1.8.2). The details of the cost estimating approach are shown in figure 69. 

Applying the approach above for the L-band cost modeling work, several assumptions were 

considered including 

• L-band provides coverage to a large continental region (e.g., United States or Core Europe) 

• Coverage is above FL180 

• System Availability of Provision (Ap) meets COCR requirements for COCR Phase II en route 

services (sans Auto-Execute service) 

• Cost elements considered include Research and Development (including system design and 

engineering); Investment (including facilities and equipment); and Operations and Maintenance 

(including telecommunications, personnel, and utility costs) 

The first order of magnitude cost estimate for implementing an L-band aeronautical ground 

infrastructure considering life cycle costs and applying the present worth simple payback method (with 

minimum attractive rate of return = 5 percent) indicates that a positive business case can be achieved 

(payback period of 4 years). While the first order of magnitude cost estimate yielded positive results, the 

important aspect of the study to bring forward was the framework of the analysis, which can be 

considered a generic framework specifying infrastructure costs associated with an L-band system. 

Additional details specific to the L-band cost assessment are provided in the FCS Phase II report, Section 

E.1.8. 

C.5 L-Band Interference Analysis 

Work on this topic was addressed in two ways. First, a modeling effort was performed to assess the 

interference effects of two candidate technologies on existing L-band aeronautical systems. This work 

was conducted as part of the FCS Phase II study. Next, as a result of the Phase II findings, an interference 

measurement campaign was conducted as part of the FCS Phase III study. A summary of the results 

relating to the analytical assessment are provided here, with details provided in the FCS Phase II report, 

Section E.1.4. A full description of the objectives, methodology, and results relating to the interference 

measurement work conducted during FCS Phase III are provided in Section 2. 

A candidate spectrum band for the future aeronautical communication radio system is the aeronautical 

L-band spectrum. This band, 960 to 1215 MHz, has a primary allocation for Aeronautical Radio 

Navigation Services. There are current several system implementations that occupy the band. 
NASA/CR—2008-214987 68

 ICAO systems that use spectrum in this band include the universal access transceiver (UAT); 

secondary surveillance radars (including Air Traffic Control Radar Beacon System (ATCRBS), Mode A 

and C, and Mode S); and DME. A majority of the spectrum allocations for these systems are standardized 

by ICAO. There are, however, some exceptions such as DME allocations defined on a national basis 

between 962 and 977 MHz in the United States. 

Additional systems operating in the aeronautical L-band spectrum include military systems. These 

include TACAN and joint tactical information distribution system (JTIDS)/multifunctional information 

distribution system (MIDS) (Link-16). The use of military systems in this band is subject to national 

coordination between military and civil authorities. Global Navigation Satellite Systems also occupy this 

band. Specifically, the upper part of the band has been designed for radio-navigation satellite service 

(RNSS). A visual depiction of the current and planned L-band utilization is shown in figure 70. 

As part of the consideration of new future communication system technology implementations in this 

band, the need to analyze the interference potential of proposed technologies to systems current operating 

the aeronautical L-band spectrum has been identified. A generic process for interference analysis would 

have the following elements: 

• Describe the source of interference and the interference mechanism 

– Description is usually in the form of power spectrum and time characteristics (e.g., transmit 

(Tx) power, transmission bandwidth, and duty cycle) 

• Quantify the isolation between transmitter output and receiver input 

– This isolation includes the effects of antenna gains, cabling losses, and propagation 

• Determine the ratio of desired to undesired (D/U) signal power at the input of the receiver 

decision process (detector) 

• Quantify receiver performance as a function of this D/U ratio, ascribe a required performance, 

and assess compatibility 

The last item noted above is the most difficult element of the process and was the focus of the 

interference simulation work defined for this study. Specifically, during consensus FAA, NASA and ITT 

deliberations at the beginning of the Phase II study, two technologies were selected for detailed analysis, 

LDL and P34/TIA–902. At that time, it was determined that the compatibility of those two proposes 

systems with existing ICAO standardized civil aviation systems would be included in the detailed 

analysis. Thus, the objective of the interference analysis task was to determine the compatibility of 

P34/TIA–902 and LDL with standardized civil aviation systems. The approach for the interference 

analysis included (for each system being analyzed) 

• Selection of an appropriate measure of interference degradation 

• Collection of information about the system (known susceptibilities and system technical 

parameters) 
NASA/CR—2008-214987 69

• Development of a physical layer system model and validation with known results 

• Introduction of the interference source and prediction of victim performance 

In an effort to prioritize analysis resources, a list of individual candidate interference analyses was 

defined. This list is provided in table VI. 

TABLE VI.—CANDIDATE INTERFERENCE ANALYSES 

Interference 

source 

Victim receiver Interference mechanisms Source 

characterization 

Has vulnerability 

been characterized? 

FRS GNSS Broadband noise Noise (WB) Yes 

960 to 1024 MHz Spurious emissions NB or CW Yes 

 1176.45 MHz Desensitization 

960 to 977 MHz 

Preferred 

 

 Mode S Broadband noise Noise (WB) Yes 

 Spurious emissions NB or CW Unknown 

 1030 MHz Desensitization 

 1090 MHz 

UAT Adjacent signal FRS dependent No 

 978 MHz Broadband noise Noise (WB) Yes 

 Spurious emissions NB or CW Yes 

DME Co-channel FRS dependent No 

962 to 1019 MHz Adjacent signal FRS dependent No 

 Broadband noise Noise (WB) Yes 

 Spurious emissions NB or CW yes 

In the table above, it can be noted that some of the vulnerabilities have previously been characterized. 

Therefore, the focus of this study was on the vulnerabilities in red, that is, those vulnerabilities that have 

not previously been addressed. 

C.5.1 DME Interference Assessment 

The DME system is an ICAO-standardized navigational aid used to determine the aircraft location. It 

consists of an interrogator located onboard the aircraft and a transponder located at a ground station. At 

regularly spaced intervals, the interrogator transmits a coded pulse to the transponder. Reception of this 

pulse triggers a coded reply from the interrogator at a different frequency. The DME system uses the 

principle of elapses time measurement between these two messages as the basis for determining the 

distance between the aircraft and the ground station, also called the slant range distance. DME 

frequencies are spaced in 1 MHz increments throughout the 962 to 1213 MHz band, providing potential 

for interference to and from FRS in L-band. A list of known susceptibilities and previous DME 

susceptibility test were reviewed. 

With the knowledge gained from review of existing DME tests, a first step in the FCS/DME 

interference analysis was the development of a DME receiver model. To perform this work, published 

data on DME interference from global positioning system (GPS) signals was obtained. The data indicated 

that interference from P(Y) and from C/A signals does not differ much, even though the P(Y) signal has 

10 times larger bandwidth. Thus a hypothesis was developed, which assumes that pulse detection in DME 

equipment is performed over a short window, on the order of one P(Y) chip length. A receiver window 

length, which would yield a match with the published data, was then computed. 

This hypothesis and associated DME architecture assumptions were applied and a mathematical 

model, which describes this architecture, was built. The model was run for different values of parameters 

to determine sets of parameters that matched published results. The implemented model was then tested 

using a UAT interfering signal to test results. The developed model and associated UAT test results are 

shown in figure 71. 
NASA/CR—2008-214987 70

For the model above, DME pulses were modeled as gaussian. UAT was modeled as a frequency-shift 

keying, constant amplitude signal. Here, the DME pulses and interference were superimposed in the time 

domain. The resulting signal was filtered using a filter with gaussian response function; the width of the 

filter response is computed to match a measured decrease of interference effect as a frequency offset of 

1 MHz as compared to no offset. 

Results captured were compared with published data and despite the seemingly good correlation of 

results of the developed model and measurements, several problems with the developed model were noted 

during validation testing. Specifically, 

• The measured results are extremely flat over the reply efficiency range of the test. 

– Indicative of an automatic gain control circuit (perhaps) or some second order effect that is 

not immediately obvious 

• To create a range of “Acquire Locks” for various reply efficiencies, the interference power for 

our model had to be varied over a 10 to 12 dB range. 

– This was deemed to be sufficiently far from measured results as to be a unreliable indicator 

(for use in predicting interference from FRS sources). 

• Several requests for information and assistance were made by NASA, but the information that 

was needed (detailed algorithm descriptions from radio manufacturers) was not made available. 

As a result of the observations above, a decision was made to not further use the developed model. 

Rather, measurements were recommended to more substantively characterize the DME to communication 

waveforms in the final phase of the FCS technology assessment. 
NASA/CR—2008-214987 71

C.5.2 UAT Interference Modeling 

UAT is a wideband data link that enhances pilot situation awareness and increases safety by allowing 

general aviation pilots to process navigational signals from the GPS, receive traffic information, broadcast 

their position, and perform other functions. It is a technology that is standardized through ICAO for 

Automatic Dependent Surveillance, Broadcast (ADS–B); Traffic Information Services, Broadcast (TIS–

B); and Flight Information Services, Broadcast (FIS–B). UAT operates at 978 MHz, providing potential 

for interference to and from a FRS in L-band. 

UAT has several known susceptibilities. These include 

• DME signal interference (basic and high-performance receivers) 

– 99 percent successful message reception of long messages in presence of DME pulse pairs at 

a nominal rate of 3600 ppps at either 12 or 30 μs spacing at a level of –30 dBm for any 

1 MHz channel frequency between 980 and 1215 MHz (desired signal >= –90 dBm) 

• DME signal interference (basic receivers only) 

– 90 percent successful message reception of long messages in presence of DME pulse pairs at 

a nominal rate of 3600 ppps at either 12 or 30 μs spacing at a level of –56 dBm for any 

1 MHz channel frequency between 979 MHz (desired signal >= –87 dBm) 

• DME signal interference (high-performance receivers only) 

– 90 percent successful message reception of long messages in presence of DME pulse pairs at 

a nominal rate of 3600 ppps at either 12 or 30 μs spacing at a level of –43 dBm for any 

1 MHz channel frequency between 979 MHz (desired signal >= –87 dBm) 

For this study, the objective was to characterize the impact of LDL and P34/TIA–902 interference on 

UAT performance. To perform the analysis, several assumptions were employed. For UAT, the basic 

ADS–B message code RS(30,18) has been modeled. And, the analysis did not include long ADS–B 

message codes RS(48,34) or Ground Uplink Message Codes RS(92,72). For LDL, the transmitter model 

used a data rate of 62.5 kbps. The analysis did not consider other possible LDL data rates. And finally, for 

P34/TIA–902, the 50-kHz channelization configuration of P34/TIA–902 was modeled. The analysis did 

not consider the 100- or 150-kHz configurations. 

Details of the UAT/LDL/P34/TIA–902 transmitter block diagrams; analysis parameters and SPW tool 

transmitter implementations are described in Section E.1.4.2 of the FCS Phase II report. The end-to-end 

simulation model is shown in figure 72. 

The model was validated using the AWGN environment and good correlation with published results 

achieved. A summary of simulation results, which include a collection of BER curves for varying degrees 

of LDL/P34/TIA–902 interference into the UAT signal, are shown in figure 73. 

From the curves above, it would appear that a carrier to interference (C/I) ratio between 12 and 15 dB 

is required for minimum degradation to the UAT receiver. LDL has slightly better performance than 

P34/TIA–902 in terms of not interfering with UAT receivers. 

C.5.3 Mode S Interference Modeling 

Mode Select (Mode S) is a system developed to phase out the ATCRBS by providing enhanced 

surveillance information for use by air traffic control automation. Mode S provides more accurate 

position information and minimizes interference by discreet interrogation of each aircraft. Each aircraft 

has its own unique Mode S address, providing a mechanism by which an aircraft can be selected and/or 

interrogated such that no other aircraft reply. Mode S also provides a digital data link to exchange 

information between aircraft and various ATC functions and weather databases. The system operates at 

1030 and 1090 MHz providing a potential for interference to and from a FRS in L-band. 

The developed Mode S transmitter simulation model exactly met the rise-time, decay-time, and power 

spectral density (PSD) mask requirements given in the Mode S MOPS. The developed simulation 

modeled the Mode S preamble detection circuit, making a hard decision on every 0.5 μs symbol. 
NASA/CR—2008-214987 72

Selectable sensitivity is also included in the model. Using the developed Mode S transmitter and 

preamble detection models, an end-to-end simulation was created. This end-to-end model included 

integrated LDL and P34/TIA–902 interferer models. Details on the simulation block diagrams and SPW 

transmitter implementations are described in Section E.1.4.3 of the FCS Phase II report. 

For both LDL and P34/TIA–902 interferences, Mode S probability of correct preamble detection and 

probability of false preamble detection were measured for several interference levels and several 

assumptions of required correlation to achieve preamble detection. To compare the interfering effects of 

P34/TIA–902 and LDL, a probability of correct preamble detection based on varying C/I values (for 94 

percent correlation and 100 percent correlation for declaring detection) for both P34/TIA–902 and LDL 

interferers are shown in figure 74. 
NASA/CR—2008-214987 73

A similar comparison of interfering effects for Mode S probability of false preamble detection is 

shown in figure 75. 

The modeling results would seem to indicate that a C/I ratio of 15 dB or better is required to not 

substantially degrade the Mode-S preamble detection performance. The behavior of “false preamble 

detection” would appear to be somewhat worse than the behavior of “missed preamble detection.” As in 

the UAT case, the performance of LDL is better than that of P34/TIA–902; that is, P34/TIA–902 acts as 

more of an interference source than LDL to both Mode S and UAT receivers. It should be noted that all 

simulations were made “on-tune;” actual deployment scenarios should be far off-tune, especially for the 

Mode S case (proposed band for the FRS is 960 to 1024 MHz, and the Mode S Extended Squitter 

equipment is at 1090 MHz). Additionally, measurements should be made that further characterize Mode S 

behavior as there are other metrics to investigate besides preamble detection. Finally, the preamble 

detection modeled is hardly sophisticated, and better performance from actual equipment is predicted. 
NASA/CR—2008-214987 74

C.6 Satellite Technology Availability Performance 

For the satellite and over horizon technology family, two technology inventory candidates have 

emerged from the technology screening: Inmarsat Swift Broadband (SBB) and Custom Satellite 

Solutions. For satellite aeronautical communication solutions, availability typically arises as an important 

issue to address. In order to provide required availability, a highly redundant custom satellite system 

architecture is needed. As this issue is similar for both Inmarsat and Custom Satellite Solutions, it was 

considered instructive to estimate the availability of two existing, operational satellite systems, Inmarsat 

SBB and Iridium, which provide services in protected aeronautical spectrum (AMS(R)S). 

The approach used for SATCOM availability modeling was the analysis model described in RTCA 

DO–270. This document defines an availability fault tree to permit characterization and evaluation of 

multiple availability elements. The fault tree is organized into two major categories, system component 

failures and fault-free rare events. This model, shown in figure 76, was useful for comparing architectures 

and was applied in this study. 

Details of the evaluation of each component failure are documented in the FCS Phase II report, 

Section E.2. A summary of availability modeling results is shown in figure 77. For SATCOM systems, 

limiting factors for availability include satellite equipment failures and RF link effects (Inmarsat and 

Iridium), capacity overload (Iridium), and interference (Iridium). For the VHF terrestrial reference 

architecture, the limiting factors for availability include RF link events and capacity overload. Overall, the 

detailed evaluation of satellite communication systems (with a focus on provision of required availability) 

indicated that both Inmarsat SBB and Iridium would not meet availability requirements. Also, a custom 

satellite solution designed to meet COCR availability requirements would, in fact, require a highly 

redundant and costly architecture. Although availability concerns may limit the use of satellites as costeffective solutions for continental airspace domains, this does not preclude their effective role in 

providing communication capability in remote and oceanic airspace. 
NASA/CR—2008-214987 75

C.7 C-band Technology (IEEE 802.16e) Performance 

C-band modeling activities were conducted to investigate the utility of an industry standard system in 

the airport surface environment. The system that was chosen for analysis was the IEEE 802.16e 

metropolitan area network (MAN) interface standard. The IEEE 802.16e standard (referred to as simply 

the 802.16e standard, or 802.16e henceforth) was chosen as it scored well during the initial phase 

(technology prescreening) of the FCS technology investigations. 

As the 802.16e standard supports a range of physical layers, prior to the modeling process, a specific 

physical layer needed to be selected. Of the possible candidates, better mobility performance is expected 

from OFDMA than OFDM, and the leading commercial 802.16 forum (the WiMAX Forum) has defined 

“mobile” WiMAX profiles, which are all expected to adopt the OFDMA physical layer. In this study, 

however, the OFDM physical layer was selected for analysis, as it seems that if good performance can be 

predicted for OFDM then by inference the OFDMA physical layer would also work well. Further, there 

are commercially available chipsets for the 802.16 OFDM physical layer currently available. Since a 

logical next step to this research would be prototype implementations and trials in the band, and noting 

that OFDM (due to the aforementioned chipset) is more amenable to prototype equipment development, 

this seemed to be a reasonable decision. 

Implementing the methodology defined above, 802.16e transmitter and receiver functions were 

modeled in the MATLAB Simulink environment. The next step in the C-band modeling work was to 

validate the developed model, as depicted in figure 78. Specifically, the simulation was executed in an 

AWGN environment and corresponding results compared to published results. Good correlation was 

achieved. Details related to the developed models and validation results can be found in the FCS Phase II 

report, Section E.3.2.1. 

Using a channel model adapted from a detailed model developed by Ohio University (described in 

detail in Section E.3.3 of the FCS Phase II report), the performance of 802.16e in the aeronautical airport 

environment was simulated as shown in figure 79. Here performance was found to be quite good for most 

of the movement area (incorporating equalization techniques). While this technology has good potential 

applicability for this domain, additional analysis to look at features to enhance performance (e.g., hybrid 

automatic repeat request (HARQ), fast feedback channel and diversity subcarrier permutations) is 

warranted. 
NASA/CR—2008-214987 76
NASA/CR—2008-214987 77

Appendix D—List of Acronyms and Abbreviations 

3GPP Third Generation Partnership Project 

ACL air traffic control clearances 

ACM air traffic control clearance message 

ACP Aeronautical Communications Panel 

ADS–B Automatic Dependent Surveillance Broadcast 

AMC ATC microphone check 

AMCP Aeronautical Mobile Communication Panel 

AOC aeronautical operational control 

APCO Association of Public-Safety Communications Officers 

ASOP acquire stable operating point 

ATC air traffic control 

ATCRBS Air Traffic Control Radar Beacon System 

ATIS Automatic Terminal Information Service 

ATM air traffic management 

ATMAC Air Traffic Management Advisory Committee 

ATS air traffic services 

ATSP air traffic service provider 

ATSU Air Traffic Services Unit 

AuC authentication center 

AWGN additive white gaussian noise 

BER bit error rate 

BSOP break stable operating point 

CDMA code division multiple access 

CHC channel coding 

C/I carrier to interference 

CN Core Network 

CNS communication, navigation, surveillance 

COCR Communications Operating Concept and Requirements 

CPDLC controller pilot data link communications 

CS circuit switched 

D-ATIS digital-automatic terminal information service 

DCL departure clearance 

DLIC data link initiation capability 

DME distance measuring equipment 

DSC downstream clearance 

D/U desired to undesired 

DUT device under test 

EIR equipment identity register 

FAA Federal Aviation Administration 

FCS Future Communications Study 

FLIPCY flight plan consistency 

FNE fixed network equipment 

FRS future radio system 

GGSN gateway GPRS support node 

GPRS general packet radio service 

GPS global positioning system 

GSM Global System for Mobile communication 

HARQ hybrid automatic repeat request 

HF high frequency 
NASA/CR—2008-214987 78

HLR home location register 

ICAO International Civil Aviation Organization 

IEEE Institute of Electrical and Electronics Engineering 

IOTA isotropic orthogonal transform algorithm 

IP internet protocol 

IPv4 IP version 4 

IPv6 IP version 6 

JTIDS joint tactical information distribution system 

LDL L-band digital link 

LOS loss of signal 

MAC Media Access Control 

MAN metropolitan area network 

MHz megahertz 

MIDS multifunctional information distribution system 

MSC mobile switching center 

NASTD National Association of State Telecommunications Directors 

NOTAM notice to airmen 

OFDM orthogonal frequency division multiplexing 

PDP packet data protocol 

PDN packet data network 

PHY physical 

PRF pulse repetition frequency 

PS packet switched 

PSD power spectral density 

QAM quadrature amplitude modulation 

QPSK quadrature phase shift keying 

RA routing area 

RLA Radio Link Adaptation 

RMS root mean square 

RNC Radio Network Controller 

RNSS radio-navigation satellite service 

RRC Radio Resource Control 

RTCA Radio Technical Commission for Aeronautics 

RTP real time protocol 

SAM Scalable Adaptive Modulation 

SBB Swift Broadband 

SGSN serving GPRS support node 

SNDCP sub network dependent convergence protocol 

TCP transmission control protocol 

TDMA time division multiple access 

TELCO Telephone Company 

TIA Telecommunications Industry Association 

UAT universal access transceiver 

UDP user datagram protocol 

UE user equipment 

UMTS Universal Mobile Telecommunications System 

URA Universal Mobile Telecommunications System Terrestrial Radio Access Network 

Registration Area 

USPTO United States Patent and Trademark Office 

UTRAN UMTS Terrestrial Radio Access Network 

VHF very high frequency 
NASA/CR—2008-214987 79

VLR visitor location register 

WCDMA wideband code division multiple access 
NASA/CR—2008-214987 80

References

1. Muraca, Peter: ATMAC Recommendations, January 2005 (documented in Data Communications 

Program). FAA, 2007. 

2. Aeronautical Communications Panel (ACP) Working Group of the Whole, First Meeting. Montreal, 

Report of the First Meeting, Agenda Item 5: Review of the Progress on the Development of New 

Communication Systems, ACP−WGW01/AI−5, June 2005. 

3. Gilbert, Tricia, et al.: Identification of Technologies for Provision of Future Aeronautical 

Communications. NASA/CR—2006-214451, 2006. 

4. Vega, Elena: Framework for Spectrum Compatibility Analysis in L-Band for FCI Technology 

Candidates, AENA. 

5. Technology Assessment for the Future Communications System. ITT Industries/NASA, May 2005. 

6. EMC Analysis of JTIDS in the 960−1215 MHz Band. Mar. 1978. 

7. MIL−STD−449D: Measurement of Radio Frequency Spectrum Characteristics. Department of 

Defense, Feb. 1973. 

8. Scalable Adaptive Modulation (SAM) Physical Layer Specification⎯Public Safety Wideband Data 

Standards Project⎯Digital Radio Technical Standards. TIA−902.BAAB−A, TIA, Sept. 2003. 

9. L-Band 3G Ground-Air Communication System Interference Study. Roke Manor, Dec. 2006. 

10. 3GPP Specifications. http://www.3gpp.org/specs/numbering.htm Accessed Dec. 14, 2007. 

11. RTCA/DO−290⎯Safety and Performance Requirements Standard for Air Traffic Data Link Services 

in Continental Airspace. RTCA, Inc., Apr. 2004. 
REPORT DOCUMENTATION PAGE Form Approved 

OMB No. 0704-0188 

The public reporting burden for this collection of information is estimated to average 1 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 Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. 

Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB 

control number. 

PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 

1. REPORT DATE (DD-MM-YYYY)

01-02-2008 

2. REPORT TYPE

Final Contractor Report 

3. DATES COVERED (From - To)

4. TITLE AND SUBTITLE

Additional Technologies and Investigations for Provision of Future Aeronautical 

Communications 

5a. CONTRACT NUMBER

NNC05CA85C 

5b. GRANT NUMBER

5c. PROGRAM ELEMENT NUMBER

6. AUTHOR(S)

Gilbert, Tricia; Jin, Jenny; Berger, Jason; Henriksen, Steve 

5d. PROJECT NUMBER

5e. TASK NUMBER

5f. WORK UNIT NUMBER

WBS 561581.02.08.03.11.01 

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

National Aeronautics and Space Administration 

John H. Glenn Research Center at Lewis Field 

Cleveland, Ohio 44135-3191 

8. PERFORMING ORGANIZATION 

 REPORT NUMBER

E-16183 

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

National Aeronautics and Space Administration 

Washington, DC 20546-0001 

10. SPONSORING/MONITORS 

 ACRONYM(S)

NASA 

11. SPONSORING/MONITORING 

 REPORT NUMBER

NASA/CR-2008-214987 

12. DISTRIBUTION/AVAILABILITY STATEMENT

Unclassified-Unlimited 

Subject Category: 04 

Available electronically at http://gltrs.grc.nasa.gov 

This publication is available from the NASA Center for AeroSpace Information, 301-621-0390

13. SUPPLEMENTARY NOTES

14. ABSTRACT

The following NASA Contractor Report documents the indepth studies on select technologies that could support long-term aeronautical 

mobile communications operating concepts. This work was performed during the third and final phase of NASA’s Technology Assessment 

for the Federal Aviation Administration (FAA)/EUROCONTROL Future Communications Study (FCS) under a multiyear NASA contract. 

It includes the associated findings of ITT Corporation and NASA Glenn Research Center to the FAA as of the end of May 2007. The

activities documented in this report focus on three final technology candidates identified by the United States, and were completed before 

sufficient information about two additional technology candidates proposed by EUROCONTROL was made available. A separate report to 

be published by NASA/CR-2008-215144, entitled “Final Report on Technology Investigations for Provision of Future Aeronautical 

Communications” will include an assessment of all five final candidate technologies considered by the U.S. agencies (FAA and NASA) and 

EUROCONTROL. It will also provide an overview of the entire technology assessment process, including final recommendations. All three 

phases of this work were performed in compliance with the Terms of Reference for the Action Plan number 17 (AP-17) cooperative research 

agreement among EUROCONTROL, FAA, and NASA along with the general guidance of the FAA and EUROCONTROL available 

throughout this study. 

15. SUBJECT TERMS

Aircraft communication; Air traffic control; Avionics; Radio communications; Technologies; Technology utilization 

16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF 

 ABSTRACT

UU 

18. NUMBER 

 OF 

 PAGES

90 

19a. NAME OF RESPONSIBLE PERSON

STI Help Desk (email:help@sti.nasa.gov) 

a. REPORT

U 

b. ABSTRACT

U 

c. THIS 

PAGE

U 

19b. TELEPHONE NUMBER (include area code)

301-621-0390 

Standard Form 298 (Rev. 8-98)

Prescribed by ANSI Std. Z39-18