ADS-B Integrated Services Enabling common airspace ......ADS-B Integrated Services Enabling common airspace sharing by global E-identification and geo-fencing for open and specific

REFERENCE: ADSBFS-IN-TASD-0046

DATE: 11.12.2019

ISSUE: 1.2 PAGE: 1/41

This document is not to be reproduced, modified, adapted, published, translated in any material form in whole or in part without the prior written permission of the ADS-B Xplore participants.

THALES ALENIA SPACE OPEN

2019,Thales Alenia Space Deutschland GmbH Template: 83230326-DOC-TAS-EN/003

ADS-B Integrated Services

Enabling common airspace sharing by global E-

identification and geo-fencing for open and specific UAS categories

WHITE PAPER

Written by Responsibility + handwritten signature if no electronic workflow tool

Alexander Pawlitzki

Verified by

Felix Böhringer

Thomas Streicher

Approved by

Felix Böhringer

Approval evidence is kept within the documentation management system.


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CHANGE RECORDS

ISSUE DATE § CHANGE RECORDS AUTHOR

1.0 07.11.2017 Document creation A. Pawlitzki

1.1 29.01.2018 Updates; reflecting discussions in ADSB Xplore consortium A. Pawlitzki

1.2 11.12.2019 Document footer updated F. Boehringer


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TABLE OF CONTENTS

1. INTRODUCTION ............................................................................................................................. 5

1.1. EXECUTIVE SUMMARY ........................................................................................................... 5

1.2. REFERENCE DOCUMENTS ....................................................................................................... 6

1.3. DEFINITIONS AND ACRONYMS................................................................................................. 6

1.3.1. Definitions ...................................................................................................................................... 6 1.3.2. Acronyms ....................................................................................................................................... 6

2. CURRENT REGULATIONS ............................................................................................................ 8

2.1. EUROPE ................................................................................................................................ 8

2.2. CONUS / USA ...................................................................................................................... 8

3. NEEDS AND CONCERNS .............................................................................................................. 9

3.1. REQUIRED FUNCTIONALITIES .................................................................................................. 9

3.1.1. UAS data link classes ...................................................................................................................... 9 3.1.2. E-Identification .............................................................................................................................. 9 3.1.3. Detect and Avoid ........................................................................................................................... 9 3.1.4. Geofencing ................................................................................................................................... 10

3.2. EXISTING SYSTEMS AND PROPOSALS ................................................................................... 10

3.2.1. Operation in VLL airspace ............................................................................................................ 11 3.2.2. Current E-Identification Proposals ............................................................................................... 11 3.2.3. Auto-Avoid ................................................................................................................................... 11 3.2.4. Geofencing ................................................................................................................................... 11

3.3. IDENTIFICATION OF REQUIREMENTS ...................................................................................... 12

3.3.1. Requirements Summary .............................................................................................................. 12 3.3.2. Main Differentiators .................................................................................................................... 15

3.4. GAP IDENTIFICATION ............................................................................................................ 15

3.4.1. Global harmonization .................................................................................................................. 15 3.4.2. Frequency planning ..................................................................................................................... 16 3.4.3. No local infrastructure ................................................................................................................. 16 3.4.4. No local service providers ............................................................................................................ 16 3.4.5. Scalable architecture ................................................................................................................... 17 3.4.6. Geofencing Service ...................................................................................................................... 17

4. PROPOSED SOLUTION ............................................................................................................... 18

4.1. DESCRIPTION ...................................................................................................................... 18

4.1.1. E-Identification ............................................................................................................................ 18 4.1.2. Detect and Avoid ......................................................................................................................... 18 4.1.3. Geofencing ................................................................................................................................... 19

4.2. SYSTEM DESCRIPTION ......................................................................................................... 20

4.2.1. Devices onboard of UAS .............................................................................................................. 20


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4.2.2. Ground Infrastructure .................................................................................................................. 21 4.2.3. Frequency usage .......................................................................................................................... 22

4.3. EXPECTED PERFORMANCE ................................................................................................... 23

4.3.1. Air-to-Air Performance ................................................................................................................ 23 4.3.2. Air-to-Ground Performance ......................................................................................................... 24 4.3.3. Ground-to-Satellite Performance ................................................................................................ 24

4.4. COMPATIBILITY AND INTERACTION WITH EXISTING SYSTEMS .................................................. 24

4.4.1. Manned air traffic ........................................................................................................................ 24 4.4.2. ATC / ATM operation ................................................................................................................... 25 4.4.3. Ground Infrastructure .................................................................................................................. 25

5. ECONOMICAL ANALYSIS ........................................................................................................... 26

5.1. CAPEX .............................................................................................................................. 26

5.1.1. UAS equipment ............................................................................................................................ 26 5.1.2. Ground equipment ...................................................................................................................... 26 5.1.3. Satellite system ............................................................................................................................ 26

5.2. OPEX ................................................................................................................................. 26

5.3. TECHNOLOGICAL MATURITY ................................................................................................. 27

5.4. TIMELINE FOR MARKET ENTRY ............................................................................................. 28

ANNEX A TECHNICAL DISCUSSIONS ............................................................................................. 29

ANNEX A-1. WAVEFORM ...................................................................................................... 29

ANNEX A-2. MEDIA ACCESS ................................................................................................. 29

Annex A-2.1 Known transmission time: .............................................................................................. 29 Annex A-2.2 (Modified) Self-organized TDMA: ................................................................................... 30 Annex A-2.3 Spread Spectrum Access: ............................................................................................... 30

ANNEX A-3. FREQUENCY / CHANNELS .................................................................................. 31

Annex A-3.1 Services and Channels .................................................................................................... 31 Annex A-3.2 Potential Frequencies ..................................................................................................... 32

ANNEX B POTENTIAL SATELLITE SYSTEM ................................................................................... 33

ANNEX B-1. CONSTELLATION ............................................................................................... 33

ANNEX B-2. SATELLITES ...................................................................................................... 33

ANNEX B-3. GROUND INFRASTRUCTURE ............................................................................... 34

ANNEX C TECHNICAL DATA SHEETS ............................................................................................ 35

ANNEX C-1. EXISTING EQUIPMENT........................................................................................ 35

Annex C-1.1 Detect and Avoid (1090 MHz) ........................................................................................ 35 Annex C-1.2 Full blown transponder .................................................................................................. 37

ANNEX C-2. CANDIDATE TECHNOLOGIES .............................................................................. 38

Annex C-2.1 Semetech SR1272 ........................................................................................................... 39 Annex C-2.2 Sigfox .............................................................................................................................. 39

1.


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INTRODUCTION

1.1. EXECUTIVE SUMMARY

The ongoing rapid evovlement of the UAS sectors poses a huge challenge for the established regulatory bodies and the entities involved in Air Traffic Management. Currently discussed solutions often result in regional and local particularities which blocks global harmonization. To ensure a worldwide, safe and smooth integration of UAS into the airspace a harmonized and simple solution is needed.

This document presents a proposal for UAS E-Identification using a UAS ADS-B implementation on a dedicated frequency. Due to avoidance of external infrastructure, this system is self-standing and could be a worldwide standard.

Furthermore, this concept proposes a universal concept for geofencing broadcast, allowing a fast and dynamic management of no-fly or restricted-fly areas.

The regulation framework for unmanned aircraft in the world is currently quite diverse and not unified. Worldwide regulations under ICAO framework apply for objects exceeding 150 kg MTOW only, whereas lighter objects are managed by regional or national entities, unfortunately not in the same way all across the world.

Currently, the vast majority of unmanned objects fall under the semiprofessional, hobby or toy class, usually below 2 to 5 kg MTOW. Objects between 25 kg and 150 kg may evolve in the future and may outnumber the “manned” counterparts. There will be cases where such craft may operate within non-segregated airspace without prior clearance and without coordination to other traffic, for example in SAR assist, early rescue, medical deliveries, reconnaissance, ad-hoc data relay applications. Currently, no real (i.e. practical) regulations exist for them. A mechanism needs to be defined and developed to cover such scenarios.

In the manned air traffic domain, several position reporting systems are possible, namely ADS-B (which is now becoming mandated for the “bigger” participants) and FLARM (more important for glider planes). It is also noticeable, that some systems evolve apart from regulation mandates (e.g. FLARM) on a voluntary basis. FLARM is a good example of a regulatory inactivity combined with a technical success, and this should become a lessons-learnt for setting up newer systems.

Establishing a common, worldwide robust position reporting system for unmanned aerial vehicles would be highly beneficial for all air traffic users. Considering the highly loaded 1090 MHz spectrum, there are good reasons for using different frequencies – but establishing links to existing systems. The rules of the air (ICAO Annex 2) are not fully practical for the coexistence of unmanned tiny craft and manned airplanes; therefore an automatic avoid feature of small craft is proposed. By using a worldwide standardized system, global interoperability of unmanned aircraft is ensured wherever they are purchased and wherever they are flown.

Geofencing – the definition of no-fly zones – becomes more and more important, especially when unmanned objects are operated in VLL where up to now no formal regulations of air traffic were deemed necessary – since this airspace is below the minimum safe altitude for classical aircraft. The definition of an electronic broadcast for no-fly areas would eliminate the need of frequent database checks. For RPAS operators, regulatory compliance is easy and “built-in” the system.

This paper has been created during the ESA ARTES Study ADS-B Xplore. Its goal is to explore the viability of integrated services using ADS-B. The study is led by Thales Alenia Space Germany supported by Egis Avia, Helios, DLR, SAP and Atmosphere.


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1.2. REFERENCE DOCUMENTS

Acronym Reference Issue Title

RD 1 EUROCAEE WG 105 1.0 E-Identification and Geo-Fencing for Open and Specific UAV Categories

RD 2 EASA Report 2 Study and Recommendations regarding Unmanned Aircraft System Geo-Limitations

RD3 EASA Introduction of a regulatory framework for the operation of drones

RD4 NATS CAP 1392 ASI ECWG Recommendation Paper: Electronic Conspicuity in Class G Airspace

RD5 Doc 10019 AN/507 1 ICAO - Manual on Remotely Piloted Aircraft Systems (RPAS)

RD6 1 U-space Blueprint, SESAR JU 2017

RD7 15/12/2015 Arrêté relatif à l’utilisation de l’espace aérien par les aéronefs qui circulent sans personne à bord

RD8 Cap 722 6 Unmanned Aircraft System Operations in UK Airspace - Guidance

RD9 ADSBFS-AN-EGIS-0019 1.0 ADS-B Xplore: Stakeholder Analysis and User Requirements Definition for the AEREAS service

1.3. DEFINITIONS AND ACRONYMS

1.3.1. Definitions

The terms UAS, UAV and RPAS are used in this document interchangeably.

Unmanned aircraft above 150 kg are generally considered as aircraft and assumed to behave like them in terms of operation, clearance, equipage etc. In the wording of EASA, they fall into the certified category.

In the scope of this document, RPAS and UAS are seen as craft below 150 kg (some of them – depending on their operation – may still be seen as aircraft), usually operating in the specific and open category. Due to practical limits, toy craft below a certain mass are excluded; the limit is not defined but proposed to be in the order of 1 to 2 kg.

1.3.2. Acronyms

Acronym Meaning

ACAS Aircraft Collision Avoidance System ( TCAS)

ADS-B Automatic Dependent Surveillance - Broadcast

ADS-B NTD ADS-B Non-Transponder Device

AEREAS ADS-B Enabled RPAS Common Airspace Sharing

AGL Above Ground Level

ANSP Air Navigation Service Provider

ATC Air Traffic Control

ATC Air Traffic Control

ATM Air Traffic Management

BLOS Beyond Line Of Sight


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Acronym Meaning

BRLOS Beyond Radio Line Of Sight

BVLOS Beyond Visual Line Of Sight

C2 Command and Control

CDMA Code Division Multiple Access (see also: FDMA, TDMA)

CPDLC Controller/Pilot Data Link Communications

DSNA Direction des Services de la Navigation Aérienne

EASA European Aviation Safety Agency

FDMA Frequency Division Multiple Access (see also: TDMA, CDMA)

FEC Forward Error Correction

FIS Flight Information Service

FPDC Fédération Professionnelle du Drone Civil

G/A General Aviation

GNSS Global Navigation Satellite System

ICAO International Civil Aviation Organization

LOS Line Of Sight

MTOW Maximum Take Off Weight

RLOS Radio Line-Of-Sight

RPA Remotely Piloted Aircraft

RPAS Remotely Piloted Aircraft System

RPAS Remotely Piloted Aircraft System

RPS Remote Pilot Station

SAR Search And Rescue

SESAR Single European Sky ATM Research

SOTDMA Self Organizing TDMA

SPOF Single Point Of Failure

TCAS Traffic Collision Avoidance System ( ACAS)

TCAS RA TCAS, Resolution Advisory

TDMA Time Division Multiple Access (see also: CDMA, FDMA)

TIS-B Traffic Information System Broadcast (relay of traffic information towards aircraft using ADS-B)

UAS Unmanned Aircraft System

UAT Universal Access Transmitter (ADS-B like system on 978 MHz)

UAV Unmanned Aerial Vehicle

UTM UAS Traffic Management

VLL Very Low Level (Airspace) (usually below 400 or 500 ft AGL)


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2. CURRENT REGULATIONS

This chapter gives an overview over different existing regulations. However it is not complete and shall outline the direction of such regulations only. It is evident, that due to the delegation to national competences a general and harmonized regulation does not yet exist – but there is a clear need for this.

2.1. EUROPE

The following White Paper will cover the Open and Specific categories according to EASA. Even if there is no formal grouping into weight classes, at least some correlation is seen (mass values given here are indicative and not referring to any definite regulation):

Toy drones <250 g. They are too small to carry significant additional equipment, their endurance is quite limited and they are not further considered here.

Hobbyist drones <2 kg. They are still small, but big enough to pose significant risk to other air traffic participants in case of near misses or collisions; they are able to carry at least some additional payload, but very limited in size, weight and power. It is expected that these craft are (usually) not significantly operated in BVLOS or long range missions.

Semi-professional craft <5 kg. Such craft are able to carry additional payload and have enough power left for its operation (Tx/Rx/positioning); however this equipment needs still to be light enough. Some operations in BVLOS or medium range could be possible.

Professional craft between some 5 kg and <25 kg. Such craft are able to carry equipment in the 100 g class. Such craft could already be operated with significant mission durations, ranges and BVLOS operation.

The range between 25 kg and 150 kg is currently rare in operation, but is expected to grow, especially when delivery UAS shall carry some payload. Current regulations do not yet consider this class according its expected economic potential. It is expected that a considerable fraction might be operated in the “specific” class therefore being subject to this White Paper.

2.2. CONUS / USA

The USA is the most important player in North America, ensuring a more harmonized regulation, but also not necessarily harmonized with the rest of the world.

Main rules are set forth in Federal Regulations, Title 14, Chapter I.F Part 1071. The regulations here are similar, but not identical to what exists in Europe.

1 Obtainable here https://www.ecfr.gov/cgi-bin/retrieveECFR?gp=1&SID=dcf7ddb5f58f33726d33d7bc50a36d72&ty=HTML&h=L&mc=true&r=PART&n=pt14.2.107.

In this paper, we focus on “Open” and “Specific”

Categories.

https://www.ecfr.gov/cgi-bin/retrieveECFR?gp=1&SID=dcf7ddb5f58f33726d33d7bc50a36d72&ty=HTML&h=L&mc=true&r=PART&n=pt14.2.107

https://www.ecfr.gov/cgi-bin/retrieveECFR?gp=1&SID=dcf7ddb5f58f33726d33d7bc50a36d72&ty=HTML&h=L&mc=true&r=PART&n=pt14.2.107


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3. NEEDS AND CONCERNS

3.1. REQUIRED FUNCTIONALITIES

3.1.1. UAS data link classes

Data exchanged between the UAS and the outside world can be divided into three classes, showing different data rates and criticality; therefore there are good reasons to separate these three classes within the UAS.

1. Identification and Position Data. This data shall be receivable and decodable by everyone in the vicinity of the UAS to find out, who is there and where it is. Such data should be transmitted / broadcasted in an automated way in clear form. Protected frequencies should be used.

2. Command and Control (C2) Link. This data is required to command and control the craft and to receive vital information on its mission; it is normally a point-to-point link between the UAS and its operator. Due to its nature, it needs certain requirements regarding availability, continuity, reliability and integrity. Loss of this link has direct safety impact. Data items of this link are not of interest to someone else. While frequencies need to be allocated in a defined way (required to meet the safety case), there is no need to standardize C2 links in terms of protocols or contents beyond what is required from the regulatory point of view. Frequencies are not necessarily similar to ID and Position broadcast2.

3. Payload data. This data link contains the mission data. Unlike the C2 link, a loss of the payload data link does not have a safety impact – some video or reconnaissance data might be lost, but the craft is still controlled. Frequencies do not need to reside in protected aeronautical band.

This White Paper focuses on the first class of data links only (Identification and Position), leaving the rest to the well ongoing activities.

3.1.2. E-Identification

E-Identification contains two elements: The identification of the UAS itself (required) and a location reporting capability of this UAS (desired if this information is available onboard the UAS). Preferably any UAS should have this capability considering its technical feasibility.

The amount of data broadcast here is similar to existing systems like ADS-B, UAT (excluding here TIS-B and FIS-B features) or FLARM; it is generally a low data rate application in the order of few 100 bits/s to kbit/s. Due to the nature of the data, there is no link / delivery management possible, relying just on broadcasts which makes this element very easy, resilient and robust at the same time.

3.1.3. Detect and Avoid

While E-Identification transmits information from the craft, the Detect and Avoid function requires two additional features: situational awareness to see what is around plus the possibility to take some actions. Detect and Avoid requires reception capability in more than one frequency band:

2 From safety case standpoint, Id and position broadcast should use different frequencies as the C2 link (but may use the same band).

UAS produce three classes of data link:

- Identification / Position - Command and Control (C2)

- Payload Mission data

Detect and Avoid adds: - reception capability

- avoid functionality


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1090 MHz ADS-B to detect manned aviation. This is a worldwide standard. The use of 978 MHz (US UAT) is questionable, since its equipage already decreases in favor of 1090 MHz ADS-B.

FLARM reception is highly desirable and even more important compared to 978 MHz UAT, since lots of UAS operate in areas where close glider traffic is present. The probability to encounter gliders in VLL airspace is considerably higher than for powered aircraft; due to their physical properties glider planes may land outside designated airports (and they are allowed to do so).

Reception of the UAS-ADS-B out telegrams to manage own deconflicting – at least starting from a specific class on.

It is advisable combining Tx and Rx functions into the same device.

In addition to the reception capability, the avoid activity needs to be managed and there is good reason to implement this in some automated way. The following obvious features need to be regarded:

Any UAS automatic avoidance shall never interfere with systems on manned aircraft (such as TCAS / ACAS); consequently, UAS shall avoid manned traffic by performing own actions only3.

Avoid activities between UAS may include some information exchange and activity coordination between these craft, but this functionality can be grouped into several classes using what is implemented in TCAS and ACAS as functional guideline4.

3.1.4. Geofencing

Geofencing is deemed as a necessary function to avoid UAS flying in prohibited airspace or restricted airspace without authorization. The concept of such airspace is well-known in manned aviation.

This White Paper proposes a way to implement an easy, fast acting geofencing concept, which would fit seamlessly into the current ecosystem using the equipment anyhow onboard the UAS proposed by the E-Identification and Detect and Avoid concepts. By using “already there” equipment, this function will not produce noticeable add-on costs nor additional work imposed to the users, nudging them softly into a “compliance by design”.

Regarding the vast number of UAS operators, especially in the private sector, and the importance of geofencing, this function is sensitive. Overregulation and overprotection typically leads to a growing number of deliberate non-compliance, drawing a significant effort into enforcement activities which are more effective elsewhere. There is public consensus that some areas are no-fly or restricted-fly, but compliance needs to be as easy as possible.

3.2. EXISTING SYSTEMS AND PROPOSALS

Any new solutions need to harmonize into existing systems. Therefore this chapter gives an overview of what is currently being proposed or already in place.

3 This should not preclude UAS from broadcasting this activity and intention. 4 This activity could be integrated into the ACAS Xa/Xu framework, for example „An Introduction to ACAS Xu and the Challenges Ahead“, IEEE paper, http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=7778055, retrieved 11/2017.

“Built-in” compliance instead of mandatory database

updates

http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=7778055


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3.2.1. Operation in VLL airspace

The operation of UAS in VLL airspace does not preclude them from encountering manned air traffic there. Even if ICAO (and national rules) mandates aircraft maintaining a specific minimum safe altitude, this is not always the case, especially due to:

Glider planes, operating on lower altitude due to their physical properties. Their occurrence in VLL is not predictable in advance, nor do they have any clearance, since they operate usually in non-controlled airspace anyhow.

Working flights operating in VLL due to their specific missions. Such flights are usually known in advance, since they need prior authorization; however this is not true for all kinds of flights. Helicopters could take off from private grounds into uncontrolled airspace without prior clearance.

SAR, Police and MIL flights. In many cases, these missions are not known in advance; they also do not need clearances or exemptions to use VLL.

3.2.2. Current E-Identification Proposals

There are currently several E-Identification trials ongoing. Due to the dynamic of the matter, the overview here is likely neither complete nor up-to-date, but the outline of all activities is clear.

France has an outline5 of a reporting mandate in place; German DFS established trials with a transmission device using the network of German Telecom.

The picture shows a non-harmonized infrastructure with lots of national or regional solutions, which are not necessarily compatible. However there is now the unique opportunity to create a global solution. Other domains have demonstrated that there will be solutions emerging – in absence of a central regulatory body such solutions might not provide the functionality or interoperability as desired. However once established they will persist making a later harmonization difficult to impossible. Therefore, the opportunity should be used to create a harmonized concept, which will be accepted worldwide.

3.2.3. Auto-Avoid

The concept of receiving 1090 MHz on UAS and perform an automatic avoid against manned air traffic is not new. However it would be ideal to extent such a system also to some avoidance or deconflicting between UAS without the need of new equipment. A collocation of similar boxes on a single UAS all dealing with similar, but different systems should be avoided.

3.2.4. Geofencing

The current implementation of geofencing is database driven. The information is published and made available and the operator of the UAS has to download this data into the UAS or its flight control.

Some predefined no-fly areas might be already hardcoded in the UAS, but to obtain a recent status a periodic update is required. This causes some delay and establishing no-fly zones over emergency or disaster areas will not be possible within that time. Also database update is – in most cases not 5 Law 2016-1428 of 24.10.2016, article 4 (at this time it is an outline only).

VLL airspace is not free from manned air traffic.

Harmonized, worldwide compatible ID system required.

Geofancing data is stored in databases, requiring regular

“pulled” updates by users.


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intentionally – not done in a timely manner, i.e. when a European traveler operates his UAS in the US or vice versa. Nearly all of them are “harmless” users – but might fail to comply with regulations even without knowing it.

In addition, database location is spread over various locations – even different for each country. It complicates an up-to-date database even more.

It is also known that this issue of violating restricted airspace is present for GA, mainly sports and recreational aircraft. This point to the “market need” (in fact, it is more a public need) to make a geofencing system simple. We won’t be able to prevent “bad guys” from entering such airspace – but making the system simple allows to concentrate enforcement activities to areas where they are really needed; the benefit in public safety and security is limited when we chase innocent travelers.

3.3. IDENTIFICATION OF REQUIREMENTS

Details on the requirements justification can be found in the respective study document of the ESA ARTES study [RD9] and are summarized in the following table.

3.3.1. Requirements Summary

Req. Id Requirement Text Comment / Justification

General Requirements

GEN1 UAS traffic regulations (identification, position reporting, collision avoidance) shall be harmonized internationally.

UAS should be usable worldwide without the need for adaptations. A logic similar to aircraft could be used.

GEN2 UAS traffic regulations shall be simple and resilient by design (no centralized vulnerable items, no SPOF).

External coordination infrastructure may be vulnerable.

GEN3 UAS traffic regulation shall be “easy to use” for the UAS user and ensure “compliance by design”.

No complicated sign-on, update etc. Open large areas of airspace in a similar way as it is the case for GA.

Position broadcast (E-Identification)

UR01 The service shall be compatible with the applicable UAS regulations (national, European and international) which will be published in the coming years.

Points to a future standardization framework. Consequently, this framework needs to be shaped having our service in mind.

UR02 All UAS shall be registered to the authorities.6 Even if this might become a national activity, the

UAS ID needs to be harmonized (like the Mode-S ID).

UR03 All UAS with an operating mass above a prescribed threshold shall broadcast their identifier, position and operation category (E-dentification) on a dedicated channel.

Threshold mass is tbd, but should be internationally harmonized.

UR04 UAS with an operating mass above a prescribed threshold should broadcast their intent on a dedicated channel.

Different “performance classes” of this broadcast system may be identified, see SYS10.

SYS01 Signal-in-space, data formats and coding of broadcasted UAS information shall be standardized worldwide.

Similar as ICAO Annex 10 Vol IV. Worldwide use of UAS.

SYS02 E-Identification broadcast shall be open (not encrypted) Receivable by all participants in the airspace.

6 From the functional perspective, even this is not required. The only item which is required is having a unique ID oft he UAS at least locally within the radio coverage. The registration ensures, that the ID tracks back to an operator; for position emission and auto-avoid functionality this is technically not required. An example for such a „volontarily“ organized registration process is the 48bit Ethernet hardware MAC.


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Mandatory for “stay clear” function.

SYS03 E-Identification broadcast service shall be self-coordinating and not requiring dedicated infrastructure to function.

No network subscription, no ground based TDMA timing; operation also when all GNSS is lost at least in degraded mode.

SYS04 E-Identification broadcast standards shall be set in a way to respect data privacy of the UAS operator as far as practical.

May not allow direct backtrace of broadcast ID to operator – at least not via a public database. Item to be discussed.

UR05 The UAS ADS-B dedicated channel shall be adapted to the small UAS operations (fly at VLL, potentially in urban areas …). It may be different from the 1090MHz if it creates a risk of saturation due to the expected growth of the UAS traffic.

Frequencies investigated in separate study. 1090 MHz likely not feasible; candidates are in 960 -. 973 MHz region or in the 5030 to 5090 MHz region.

UR05a The used frequency shall be assigned by ITU for aeronautical location purpose as primary service.

ISM frequencies offer no protection against other (legal) users!

UR07 The ADS-B out transmitter installed on the RPA shall have sufficient power to send signals to an ADS-B receiver on a satellite on low Earth orbit, but limited to avoid saturating the frequency.

This might be out of scope for very light UAS; subject to detailed analysis in separate study. Feature is demonstrated to be technically possible (ADS-B, @ 2 W / 100 g)

UAS Tracking / “Surveillance” (local, national, regional and global)

SYS10a A regional (or national) receiver network shall collect the position data for use in national framework (national UTM service provider).

Structure like national ATC.

SYS10b A global receiver network (including satellites) should collect global situational awareness. Local receiver networks may be used to feed this system (global UTM service provider or association of national ones).

Global service (like Aireon on ADS-B) or at least for FABs.

SYS10c Locally independent receivers may be used additionally for a local situational awareness service (not connected to UTM service provider)

Allows situational awareness without additional infrastructure; robust stand-alone system.

UR11 The service shall have a prescribed level of availability and, in case of a loss of service, shall warn the users within a prescribed maximum time.

This is more to establish a framework comparable to different surveillance performance classes as known in ATM. Performance may vary upon region.

SYS11 A standard protocol shall be defined to communicate UAS position and status data towards ATM

Any UAS / ATM connection should be standardized (preferably ASTERIX or JSON)

UR12 In case of RPA incursion in ATC airspace, the UTM service provider shall warn the local ANSP and provide him with the UAS information (identifier, position and operation category).

Contrary to the “airspace user”, the ANSP should be able to trace the UAS operator out of the UAS ID in order to contact him.

UR13 The service shall operate worldwide. Points to SYS01; regional specialties must be avoided.

UR14 The satellite constellation supporting the service shall have worldwide coverage

Detailed constellation investigation in phase 2 of the project.

UR15 The UAS shall be able to determine their current position (4D) with a GNSS system.

See following requirement.

SYS12 The performance UAS self-position determination capability may vary between different UAS “classes”

Performance classes to be defined; guideline could be EUROCAE WG-105 material.

UR16 The GNSS receiver used inside the UAS should be multi-constellation and SBAS.

This could also enable multi-constellation integrity (RAIM) monitoring.

Detect, avoid and stay-well-clear

UR17 UAS shall avoid, in a highly automated manner, manned air Equivalent to RA on TCAS (“take action”, but no


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traffic and other UAS via a detect-and-avoid function coupled to their autopilot system.

communication with real TCAS!)

SYS13 UAS should transmit information of detected proximity traffic towards the RPS

Equivalent to TA on TCAS (“inform”)

UR18 UAS shall be equipped at least with an ADS-B in dual-frequency receiver to provide “detect, avoid and stay well clear function” with both manned A/C fitted with ADS-B transmitter on 1090MHz and other UAS.

Details tbd. UAS shall not interact with manned traffic in TCAS-like manner, but they may establish a TCAS like system between themselves.

UR19 UAS may have to be equipped with an ADS-B in multi-frequency receiver to provide “detect, avoid and stay well clear function” with both manned A/C (including glider or GA on UAT or FLARM) and other UAS.

UAT is a standard which is under “RTCA control”. FLARM is outside the aviation world and therefore difficult to reference to.

SYS14 The UAS ADS-B in receiver should be combined with the E-Identification device.

No-fly areas and Geofencing

UR24 ADS-B NTD beacon shall identify the No-Fly zone by using the 1090 MHz or the “UAS ADS-B” dedicated channel.

Currently not standardized. 1090 MHz frequency has the benefit, that this feature can also be used by GA.

UR25 The UAS shall be equipped with an ADS-B in receiver which is able to receive signal from an ADS-B NTD beacon.

… identical to the “stay-well-clear and auto-avoid” receiver, combined function!

UR26 The UAS shall warn its remote pilot by an aural and visual alert that it is entering into a no-fly zone.

Note: There might be cases, where entering an UAS into a no-fly-zone is desired.

UR27 The UAS should relay any received no-fly zone information towards its pilot to be displayed on the control interface.

C2 link monitoring Requirements here do not specify the C2 links as such, they address only items inside the C2 link relevant to E-Identification

or UAS service itself.

UR28 The UAS ADS-B out transmitter shall continue to broadcast the UAS identifier and position in case of a loss of control by the RPS.

UR29 The UAS shall have an internal C2 link monitoring system in order to detect a loss of C2 link.

(relevant for next requirement)

UR30 The UAS ADS-B out transmitter shall be able to send a specific emergency code in case of C2 link loss detection in order to warn the UTM service provider of the UAS control loss.

UR31 In case of loss of navigation source, the UAS shall still broadcast a signal on its UAS ADS-B out frequency indicating this status (allows still signal tracking). Position data could either be “stale” or “blank”, but needs to be flagged as such.

UR32 The UAS shall broadcast the status of its C2 link in the UAS ADS-B out message

UR33 The UAS ADS-B out transmitter should have its autonomous power supply in case of a loss of the UAS main power supply.

UR34 The UAS ADS-B out transmitter should continue to broadcast the UAS identifier and last position in case of emergency landing.

Non-functional requirements for equipment onboard of UAS

UR06 The ADS-B out transmitter installed on the RPA shall have a limited size, weight and power consumption to remain

“Low weight / size” to be defined; see also Task 2 for details.


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consistent with the UAS technical specifications.

UR08 The transmitter installed on the RPA shall be low cost “Low cost” to be defined.

UR09 The transmitter installed on the RPA shall be able of operating without causing interference to other systems installed on board the RPA or systems not linked to the UAS (for example, using an adjacent channel for emission or reception).

Obvious requirement, but in reality somehow demanding due to the small size of UAS and resulting antenna collocation. Conformance tests and requirements (e.g. CE) to be detailed in task 2.

UR10 The transmitter installed on the RPA shall receive full weather proofing and shall be capable in low and high temperatures as it may be fully exposed to the elements.

e.g. -40°C to +70 (+90)°C. IP67 is desired.

UR20 The UAS ADS-B in receiver shall be little size and low weight proportional to the UAS size and weight.

UR21 The UAS ADS-B in receiver shall be low cost.

UR22 The UAS ADS-B in receiver shall be full weather proofing and low and high temperatures capable.

UR23 The ADS-B reception on UAS shall not be degraded by other RF equipment on-board the UAS (regardless of what nature, C2 or payload data link)

3.3.2. Main Differentiators

The main differentiators between this proposed “service” and other currently discussed solutions can be found in the following areas, which will be further addressed in the Gap Identification presented in the next chapter:

The main elements of these functions work without a centralized service provider. The “service” consists in provision of a harmonized specification and mandating a set of basic functions. The specification ensures technical interoperability.

The main elements are designed in a robust way not requiring any local infrastructure. GNSS is used as position source (but constellation agnostic, i.e. could be GPS, Galileo, GLONASS, Beidou or something completely different), but the “backup” functionality of broadcasting the ID only will even work without position source. Even if globally scoped, centralized assets (network control, timing) are not needed for the basic functionality.

Additional elements can be part of an add-on service on national, regional or global basis. This is seen as an independent add-on allowing the lower level realization prior to availability of a high level service.

3.4. GAP IDENTIFICATION

3.4.1. Global harmonization

The current activities diverge somehow locally. Several regions start their specific activities, this might lead to a system which lacks worldwide interoperability. In Europe, EASA leads some standardization activity, however regulations currently in place differ nationally. Since traffic and industry operates worldwide, harmonization is a must. Even if drones alone might not (yet) cross the oceans, their operators do and use these craft all over the world. Instead of mandating complex “sign-in” procedures it is

Everywhere in the world – regardless where bought and

where operated


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highly desirable to make them compatible all over the world – which is already state of the art in the market of cars, manned aircraft, sea craft etc. Lessons learnt from other domains (personal radios etc.) showed clearly, that lack of global harmonization does not prevent them from being used globally – with all the consequences following this.

3.4.2. Frequency planning

A major consequence of global harmonization is the frequency to be used. Using ISM frequencies (or license free frequencies) is on the first glance an attractive choice; however such frequencies suffer from protection between the users. Due to the huge number of expected users and the limited spectrum, the allowed output power is limited making them critical for long range communications or broadcast. Usually EIRP is very limited on those frequencies (well below 1 W) or they suffer from severe limitations (5 GHz requires radar presence detection and shut-off their transmitters in some cases) – which are not acceptable limitations for safety critical applications. Some bands are shared with primary users7 having much higher power allowances – which makes the service unpredictable in some regions.

Using a frequency “free of charge” does not limit the bands to ISM or global license free bands. National authorities may allow also the use of specific devices on other bands (permanent use requires compliance to the frequency allocation harmonized with ITU) without the need to pay a license fee. Clearly, the use of specific bands – e.g. for aeronautical mobile – requires a minimum of quality control for the devices used there, but this can be kept simple.

3.4.3. No local infrastructure

Safety critical services need to be robust and resilient. Consequently, their requirement to local infrastructures should be minimum. Especially UAS may be operated in remote regions due to various reasons, and here little to no supporting infrastructure might be present.

Existing systems in ATM like ADS-B in its various flavors showed, that a self-organizing system results in a highly robust system. A local ADS-B receiver will deliver local situational awareness – even without internet connections, Flightradar24 account or mobile internet connectivity.

The requirement for no local infrastructure also allows an easy expansion of any “service” towards remote areas. Establishing and maintaining coverage for large areas in VLL requires nevertheless a considerable number of stations, especially in difficult terrain. Covering the full Australian continent with 50 VHF towers is possible at FL300 – but impossible for levels close to ground.

The requirement for no local infrastructure does not preclude from establishing some infrastructure at selected places to improve the functions – e.g. close to critical areas like airports, MIL sites or industrial sites of high importance. However everything will continue to function even if the local add-ons are not present at all.

3.4.4. No local service providers

The basic service – who is out there? – is possible without any infrastructure at any place in the world. Even with loss of all GNSS navigation systems, we have

7 The ITU term „primary user“ of a frequency denotes that this user may use the frequency and must not be disturbed by any other, especially secondary user. „Secondary users“ must tolerate any interference caused by primary users and have no guarantee, that the frequency is available without interference.

No protection of ISM frequencies!

Self-standing operation – no infrastructure

No data plan, no service contract


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at least an ID broadcast, which could be roughly located. No “registration” to the frequency is required, no data plan, no login.

From the safety perspective, if does not care, if the craft’s operator has paid for the data plan or is registered in country-X’s network – everything which is in the air is indicating by transmission that it is there.

However the system is scalable in a way, that national, regional or global aggregation can be performed by service providers. For specific locations, i.e. a single airport, this “service” is in its simplest way a reception station only – however it can also be a more complex organization and collaboration of different service providers with different service “flavors”, as we have it in current ADS-B services.

3.4.5. Scalable architecture

The system described in this paper does not preclude any service operators. There might be global services – up to the ultimate concept of a satellite based coverage for very remote areas. However this is fully independent from local implementations, so that they may start earlier but still with the perspective to fit into a global picture.

3.4.6. Geofencing Service

The easy provision of Geofencing data is a real value added service. Current proposals call for a database, which is fed by then local authorities and maintained at centralized locations. It also identifies the need for UAS operators to keep their local databases up to date in a periodic way. The logic behind is taken from the manned aviation – every pilot shall check the applicable airspace structure and NOTAMs before flight.

In reality, the situation becomes more difficult dealing with a large number of UAS pilots, including those operating small craft in the Open category. It also should be noted, that at some time travel with UAS (meaning that traveler will carry their UAS to their travel destination and use it there – as toy, photographic platform or for whatever purpose) and their “pilots” might not always be familiar with the up-to-date restricted areas. The easiest and most elegant method here is to provide the required information free of charge using equipment which exists anyhow and which is presented automatically at the time when needed.

Therefore, it is proposed to broadcast this information additionally using ground based transmitters located in such areas. This signal is then automatically received by the UAS in proximity and can be decoded appropriately. The detailed reaction of the UAS is not subject of this White Paper and needs separate analysis; however the (up-to-date) information is available and can be at least visualized and relayed to the operator. Up-to-date data is ensured by design. Furthermore, no-fly-zones or restricted-zones can be established on the spot without the need of database entry and UAS download; this proposal is a kind of “push service” integrated in the E-Identification framework.

When standardizing this information and using for example reserved DF18 ADS-B frames, this restricted airspace information can also be available to manned aviation, especially sports and recreational craft, which are also sometimes not complying to restricted airspace – simply because they haven’t read the NOTAMS. Using the proposed service, they just get the information up-to-date in real time.

Provide geofencing information over the air

instead of mandating users to update databases.


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4. PROPOSED SOLUTION

4.1. DESCRIPTION

The solution we describe here shall be a simplistic, but effective approach to fulfill the requirements above. The root of the idea lies in current successful systems installed in manned aviation – namely ADS-B, UAT and FLARM.

4.1.1. E-Identification

E-Identification data relates to Class 1 of the above mentioned data. The content transmitted here is quite similar to what is transmitted in avionic systems like ADS-B, UAT (excluding the “extra” features) or FLARM. The proposed solution would therefore:

Use a device for periodic clear broadcast of the UAS ID, its position (if known) and some crucial data (velocity, intent, C2 link state, emergency). From its nature it is “ADS-B” (the frequency is not specified here), therefore this element could be referred as UAS-ADS-B or Drone-ADS-B.

Like the “classic” ADS-B, the information is automatically and unconditionally broadcast without the need of any terrestrial infrastructure for network access, management, timing etc.

Like the “classic” ADS-B, the information is broadcast on a frequency already allocated for aeronautical radiolocation ensuring an international harmonization.

Devices providing this functionality can be small and lightweight so that a basic E-Identification would be possible for very small craft, starting well below 1 kg of mass.

Regarding the items above, the E-Identification does not provide a centralized service provider; the “service” is to provide the information in a clear and easy way.

If GNSS is available and if the UAS is exceeding a specific envelope, the position information shall be part of the identification. However, the ID transmission shall be present even if GNSS information is not obtainable due to whatever reason, since this can also include GNSS jamming cases. In such scenarios, the UAS is still locatable by “classic” means, like AoA or hyperbolic TDOA methods, which can be used in the vicinity of sensitive ground infrastructure like airports.

4.1.2. Detect and Avoid

Detect and Avoid adds two functions to E-Identification: Reception and Action. This is not new and there are already devices available, which provide this subfunction for “classic” ADS-B on 1090 MHz with standardized interfaces to autopilots. The proposed function here will be an addition, since it combines the already existing functionality on 1090 MHz with the new E-Identification, very likely on a different frequency. Several other existing frequencies might be included (UAT, FLARM), which is in the age of software-defined-radio technology not an issue. The service behind here is also mainly in providing a regulatory framework ensuring interoperability between the technologies.

The technically more interesting feature is the auto-avoid implementation against different classes of traffic. The following functions are obvious:

No “service provider” required; information is presented by

simple broadcast.


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Auto-avoid functionality may not be present in very light crafts (e.g. sub-kg class), especially when they have no significant on-board autopilot function8. Such craft will usually be operated in close proximity to the UAS pilot and therefore likely not encountering other air traffic.

There shall be no interaction towards classical TCAS / ACAS in order not to interfere with these systems. Due to the safety crucial nature of TCAS / ACAS and active coordination would require certification and testing overhead, which is not justifiable for UAS subsystems. Consequently, UAS should avoid manned air traffic “silently” – but nevertheless in a safe and predictable way. This “predictable” way shall be compatible with existing algorithms in TCAS and ACAS, therefore involvement of the relevant groups is required.

Several UAS may communicate between each other and may implement some TCAS / ACAS like communication. This is especially of importance for craft operating BVLOS and / or operating on pre-programmed tracks. The classical mutual-see-and-avoid concept is difficult to implement. The ICAO rules of the air are formally in place, however designed at a time where UAS did not exist. The different types of UAS along with lots of unknowns in their operation make the specification and development of general avoid-algorithms difficult. There are good reasons for defining a communication interface between UAS – at least exceeding a specific envelope. However it is expected that there will be some more time required to define and refine the algorithms behind.

The proposed auto-avoid function here does not interfere with operation of UAS according to specific rules or clearances, which would be required in BVLOS at least in some cases. The transmission of the data, commands or telemetry required for this does not take place on the E-Identification frequency or within this framework. The auto-avoid proposed in the White Paper is more like the classical TCAS and ACAS considered as last safety net when other methods fail due to whatever reason. Therefore, it should be kept separate.

One real service element can be realized in monitoring the whole population analyzing occurrence of critical events which lead to separation loss, infringements, deviations from clearances and so on. Even if this requires no immediate attention, a past analysis can help top improve the system and implement newer algorithms in future UAS (or even update existing ones).

4.1.3. Geofencing

The Geofencing service is more a public service to airspace users. Instead of maintaining databases which need to be transferred somehow into the UAS or into their control system, the information is available up-to-date over the air. Due to the safety critical nature of geofencing, this information shall be provided free of charge to everyone “interested in”.

Therefore, this service can have two “customers”:

UAS operators. A dedicated frequency for this service could be considered, best in a band where UAS are already receiving. 1090 MHz is one candidate, since UAS shall already receive ADS-B there and implement auto-avoid functionality. Consequently, reception of geofencing data is possible without any additional hardware. Alternatively, a separate frequency can be considered, however this will cause additional effort for the low-end UAS, since they might not have a dedicated receiver here. All medium to high end UAS shall carry an UAS ADS-B receiver in any case, therefore for them there will be no additional effort.

8 An existing „stabilizer“ system which provides level and attitude keeping might not be able to accept avoid inputs from external devices.


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General Aviation pilots. They share large portions of the airspace with the UAS and many restricted zones or no-fly-zones span across airspace used by UAS in VLL and G/A in next higher level. A common medium to broadcast this information will therefore also G/A enable to profit from this service without any additional equipment. For this reason, transmitting this information on 1090 MHz as a kind of “FIS-B” service could be considered.

Distributing geofencing data on 1090 MHz would use the existing standard of NTD (non transponder devices); there is already a data frame reserved for them as DF18. In earlier phases of ADS-B, there was the discussion of establishing “obstacle beacons”, which was given low priority to their sheer number and consequently polluting the spectrum, but there are still activities in this domain. So NATS used ADS-B beacons on cranes to indicate their position9 (which is in fact also a kind of a no-fly-zone). The ground devices are ADS-B low power devices, which have an output power of 30W.

4.2. SYSTEM DESCRIPTION

4.2.1. Devices onboard of UAS

Due to the potential of signal processing technology, devices can be extremely small making them available to very small craft. Also, a multi-frequency receiver or transmitter is realized in an easy way and does not cause significant technological limitations.

The main difference to other proposed systems is the fact having an independent service, not requiring any infrastructure on ground (e.g. mobile network, TDMA access, channel subscription etc.).

EUROCAE WG-105 [RD1] already states the concept of several equipment and performance classes, which could transform into the following table:

Item Class I Class II Class III ClassIV

Functionality

E-Identification (Tx)

E-Identification (Rx) (optional)

GNSS receiver

ADS-B In (manned) (optional)

Interrogation10

Capable

() Limited

Manned Auto Detect & Avoid

Report Traffic11

(optional)

UAS Detect and Avoid Report Traffic (optional)

Report Traffic only to operator

() Limited

Performance

9 See http://www.airport-technology.com/news/newsuk-nats-deploys-safety-beacon-on-crane-to-enhance-aircraft-safety-4918327/. 10 “Interrogation“ means the capability that a communication between two UAS is possible to negotiate deconflicting or other parameters. This includes also the dedicated interrogation of parameters by ground stations within the radio range. 11 „report traffic“ means relying this information via the C2 link to the operator on ground taking no autonomous action.

http://www.airport-technology.com/news/newsuk-nats-deploys-safety-beacon-on-crane-to-enhance-aircraft-safety-4918327/

http://www.airport-technology.com/news/newsuk-nats-deploys-safety-beacon-on-crane-to-enhance-aircraft-safety-4918327/


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Item Class I Class II Class III ClassIV

Id reporting [s] 30 15 5 1

Position reporting [s] N/A 15 5 1

Position accuracy [m] N/A 30 10 2

Certification Philosophy

SWAL N/A N/A 4 3

Regular Test No Inflight monitoring by ground systems.12

Periodic Approvals No No Indirect13

Yes

Communication Range

Classic ADS-B In [nm] (5) 10 20 50

UAS-ADS-B In [nm] (0.5) 1 2 5

UAS ADS-B output power

14 [W]

0.5 1 10 (low power)

70 (class A0)

Detection Range by Ground Stations [nm]

1 2 5 10

Detection possible by Satellite

() Limited

Size, weight and Power design target

Weight 5 g 15 g 30 g 50 – 100 g

Power (average) 150 mW 500 mW 1 W 2 – 4 W

Table 4-1: Notional Equipment classes

Any C2 or payload data device is separated from this E-Identification / Auto-Avoid device. Any payload data link will also use dedicated equipment.

4.2.2. Ground Infrastructure

There is no ground infrastructure required for the service to operate (similar to ADS-B); however a ground infrastructure makes this service available to airport users and others. Two types of ground infrastructure are possible:

Locally installed receivers, not meshed together for a local situational awareness. Could be set up quickly and deliver situational awareness.

Meshed system with lots of receivers operating on a regional or global scale – as we have with FlightRadar24 or similar. UAS position data can be sold to users like it is done for ADS-B data.

12 If ground systems detect performance violation or malfunction, this is reported to the operator requiring correction. 13 „Indirect“: Ground Systems monitor flights and do implicit performance verification. If records are available this substitutes a periodic test. Information available for UAS operators free of charge. 14 Power level given as equivalent to a „classical“ ADS-B signal; the actual output power will be lower when more an efficient waveform is defined. Values shall be seen as reference to compare with other existing avionics. It does also not mean, that AUS ADS-B is necessarily on 1090 MHz (which is very likely not the case)


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4.2.3. Frequency usage

Frequency usage is a delicate question due to the scarcity of the spectrum.

The use of ISM / SRD frequencies is not recommended, since:

Many ISM and SRD frequencies are not coordinated worldwide and differ between the ITU regions

ISM and SRD allocations are on secondary basis only, i.e. interference must be tolerated and devices must not cause interference to primary users. This is not an option for UAS position reporting nor C2 link.

Consequently the use of aeronautical frequency shall be considered, since they are on primary allocation. Among several possibilities, two candidates have been identified:

Lowest portion of the L-Band (960 to 970 MHz), but needs to compete with LDACS. The number of DMEs is very low there; signal design can consider mutual robustness so that co-existence is possible at least for some time. Due to technical evolutions, DME could be relocated. As a technical benefit, a receiver capable of receiving 960 to 970 MHz can use the same antenna and frontend to receive 1090 MHz ADS-B as well.

MLS band (5030 to 5091 MHz). In fact, MLS is rarely used so that large portions of this band might be allocated.

Equipment for both frequencies is widely available, since current SDR transceivers are usually wideband ranging from a few 100 MHz up to 6 GHz.

Frequency [MHz]

ITU status Candidates [MHz]

Comments

Aeronautical Frequencies

960-1164 Aero Mobile, Aero Radionav 960 – 970 Consider current LDACS use; some DME might be present.

1164-1212 Aero Radionav, GNSS None Not usable due to simultaneous GNSS usage.

5030-5061 Aero Mobile, Auro Mobile Sat, Aero Radionav

5030 – 5090 MLS hardly used, could be “recycled”.

5091-5250 Aero Mobile, Aero Mobile Sat, Aero RadioNav

(tbd) Some UAS C2 link proposals within the subband 5150 to 5250 MHz, 5 GHz WLAN (5150 – 5350)

Other Frequencies

433-434 Amateur (P), ISM R1 only (S) none Too crowded; ISM Region 1 only

868 IMT (not harmonized), SRD None Europe only; low power. FLARM 868 MHz

902-928 ISM R2 only None Region 2 only

2400-2500 ISM None Worldwide ISM, but crowded (WLAN, BT, µwave)

5725-5875 None Shared with Amateur

Table 4-2: Potential frequencies for UAS ADS-B and their usability

Use protected frequencies!


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4.3. EXPECTED PERFORMANCE

4.3.1. Air-to-Air Performance

Small UAS have quite limited ranges and their operation profile is usually slow, so that their “area of interest” is in the order of a few nm only. However they are fast enough and other airspace users are fast enough, so that typical ranges demonstrated by FLARM equipment15 are at least required.

Slightly higher air-to-air reception ranges are required for the auto-avoid function against manned air traffic due to the higher criticality (= more design margin) and higher velocity of approximating manned air traffic. Basic guidelines could be taken from TCAS material16 but with the modification that the UAS takes avoid activity only and without coordination with the “intruder” and the fact that – of course – RA / auto-avoid activities shall take place below 1000 ft above ground level (AGL), which is the main operating area of UAS.

Figure 4-1: TCAS protection volume (source: FAA, footnote 16)

Typical operating speeds by manned air traffic here is around 120 kts (220 km/h), peak17 is assumed to 180 kts (330 km/h); UAS will likely stay below 120 kts in any case. Worst case closure speeds are then 300 kts, equivalent to 5 nm travelled per minute.

Situational awareness should – at least for bigger craft – add a safety factor of 2 - 4, so that a 10 to 20 nm range in any cases is the baseline for situational awareness in terms of ADS-B reception. This is not a technical issue – even poorly designed ADS-B receivers or inadequate antenna solutions will fulfill this requirement.

The other way round – detecting UAS ADS-B transmission by airborne users – here we have a subset of users only like MIL, SAR etc. – does not require this range; VLL users are assumed to operate with considerable lower speed when in VLL. Therefore detection ranges UAS aircraft of some (target 2 - 5) nm is sufficient.

15 FLARM claims radio ranges of 10 km for „PowerFLARM“ equipment, which makes at least some use of directional antennas. Since many UAS operate stationary and due to their profile, they can instantaneously maneuver into any direction, full omnidirectional broadcast is required. 16 See https://www.faa.gov/documentLibrary/media/Advisory_Circular/TCAS%20II%20V7.1%20Intro%20booklet.pdf, which is also used for the figures within this section. 17 The formal speed limit below FL100 is German „unprotected“ airspace is 250 kts.

https://www.faa.gov/documentLibrary/media/Advisory_Circular/TCAS%20II%20V7.1%20Intro%20booklet.pdf


DATE: 11.12.2019





4.3.2. Air-to-Ground Performance

Air to ground performance is relevant for detecting UAS by stationary receivers on the ground, e.g. to get situational awareness around airfields or sensitive MIL / industrial areas. Here the issue is not the total range, since this is from the point of link budget not an issue. It is more the fact, that terrestrial receivers may not have sufficient coverage into VLL areas, where the UAS might operate. Where frequencies of 1 GHz have at least some coverage into non-line-of-sight areas, this is almost impossible for frequencies in the 5 GHz range. Due to practical reasons, not every ground receiver can be positioned on a high tower, leaving some gaps, especially in built-up areas.

Unlike air traffic, which does usually not take-off nor land in densely populated areas, UAS are expected to do so. Therefore a departing UAS behind a building is a common case. Therefore ground based receivers will never be able to cover down to the ground, except we have a huge network of them, realized by voluntary participation for example over the internet – as we have on FlightRadar24, FlightAware, ADSBExchange etc.

Nevertheless, air-to-ground performance should be sufficient to create enough situational awareness around airports and sensitive areas even with the identified restrictions. A typical detection range for “high flying” UAS – which is considered to be 250 to 400 ft AGL – for such stations should be in the order of 10 nm with direct LOS.

4.3.3. Ground-to-Satellite Performance

The reception of “classical” ADS-B signals originating from A1S aircraft transponders (output = 125 W) is already sufficiently demonstrated by Aireon and other trial systems – even using the un-optimized ADS-B PPM waveform on 1090 MHz. Therefore, the same performance is feasible with UAS ADS-B, even considering here the possibility to create a more efficient and robust waveform.

At least for the highest output class, which is applicable for the heavier specific class UAS, a satellite detection should be possible; it is also assumed that only those UAS will operate for extended time in BVLOS and may operate in airspace, where at least some manned air traffic has to be expected.

4.4. COMPATIBILITY AND INTERACTION WITH EXISTING SYSTEMS

4.4.1. Manned air traffic

The proposed system is fully compatible with manned air traffic and will not affect their systems in any way; especially when UAS don’t use 1090 MHz for transmission.

The only interaction with manned air traffic is a “positive cooperation” realized by the UAS auto-avoid function when detecting ADS-B signals from manned air traffic. This function could help improving the equipage rate of small aircraft with ADS-B transponders, since there is no general mandate for them in place. However this evolution is anyhow strongly desired, so that this proposed system could assist it.

No impact to systems in manned air traffic


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4.4.2. ATC / ATM operation

Currently, ATC does not control UAS operation18 in any way. Clearly, there is some need to “control” and “separate” UAS traffic with manned air traffic. The concept of keeping them in fully segregated airspace might not be possible for extended time, especially when the UAS traffic is increasing.

Considering usual speeds in the order of 90 to 120 kts for regular airplanes, small objects with “visual cross sections” of 20 cm squared are hardly detectable for an airborne pilot. An object of 20 cm will appear at a distance of 250 m on an angle of 3’, which is close to the optical resolution of the unaided eye, but a typical aircraft travelling with 90 kts would collide with such an object within 5 seconds. Objects on direct collision path are hard to detect, since they have little to no angular movement and become noticeable at distances only, where escape maneuvers are already impossible. The situation on the other way round has similar challenges: The UAS pilot – being on ground – cannot reliably detect a low flying aircraft early enough to bring his UAS out of the way. This is even not possible, when the approaching aircraft uses the minimum safe altitude (500 ft) or even below, since we have to assume, that the approaching aircraft may appear behind trees, hills or buildings and might be a silent glider plane. We should also note as described above, that the VLL airspace is not free from air traffic – even outside CTR areas of aerodromes.

Since mutual see-and-avoid concepts are difficult, the first step is to improve situational awareness. Exactly this is performed by the proposed service. Future concepts need to be refined, but situational awareness is key for everything.

Aircraft operating frequently and “unplanned” in VLL airspace might add additional UAS ADS-B receivers to improve their situational awareness.

4.4.3. Ground Infrastructure

Increased UAS traffic and its detection have inherently consequences. There is the need to detect those objects around important locations like airport or MIL spots. Since their equipment is fully separated from the manned aircraft in terms of frequencies, a separate receiver infrastructure is required.

Having a harmonized system, this separate infrastructure can be created in a simple way:

In the age of software-defined-radio systems, standard ADS-B receiver may implement an additional “channel” receiving the UAS signals. When this is globally harmonized, this can be a global product and therefore globally characterized.

Necessary links between ATC systems and UAS detection receivers (where the result is being transferred) are within the scope of competent working groups laying down the baselines. There is no involvement of complex additional infrastructures making all cases more complicated.

Clearly, a frequency for UAS transmissions needs to be identified, creating some issues with legacy systems. However this is not specific to this particular service; there are already ongoing discussions of re-using the MLS band (5030 to 5090 MHz) or portions of the L-Band (lower end, 960 to 973 MHz) for this purpose.

Using a dedicated UAS ADS-B frequency produces by far less impact than using the existing 1090 MHz reporting for UAS, which is sometimes mentioned, especially in countries having low traffic density. Technical details are already described in the frequency usage chapter above.

18 Please be aware, that within this White Paper only UAS below 150 kg are considered; everything above is considered to be „manned air traffic“.


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5. ECONOMICAL ANALYSIS

5.1. CAPEX

5.1.1. UAS equipment

Due to the large number of devices for the UAS, the CAPEX can be kept very low. Since the “framework” of such devices is already on the market, only the delta development to incorporate the specific additional UAS ADS-B feature needs to be added, limiting the development costs.

Finally, the costs for UAS equipment for the lowest classes and categories should be within some 10’s of Euro / Dollars; but this is totally within range. Current smartphone chipsets have the required capabilities here and are available for less.

More elaborated UAS equipment could go beyond this, but a cap of 100 Euro should not be exceeded, even for the heavy specific category equipment.

5.1.2. Ground equipment

Ground equipment consists of two types:

Receivers / receiver network to receive the UAS ADS-B signals in order to have situational awareness what is around. In case such receivers will be used for ATM / UTM they need some level of certification.

Transmitters (ideally collocated with receivers) to broadcast the geofencing information. Unlike receivers, which can be operated by anybody, transmitter operation needs to be regulated and transmitter products need to be more carefully certified.

5.1.3. Satellite system

A satellite based service is foreseen for the larger specific category UAS, but not to be put in place at the beginning in FOC. Such services should be established in a stepped approach, but nevertheless they need to be foreseen at the beginning of the signal definition, otherwise we have the risk of incompatibility.

Stepped approach would be:

Proof of Concept with one or two microsats, not establishing a real-time service. Timeline: three to five years (2021 to 2023), mission duration one to three years.

Proof of concept, IOC over selected areas with HAPS (could be separate study)

IOC with microsat constellation using the lessons learnt from the PoC campaign. IOC in the 2027 timeframe.

5.2. OPEX

For the UAS users, no OPEX cost will occur, since there is no need for any contract or data plan. The frequency can be used free of charge (even if it is protected spectrum).

The question if heavier specific category craft would require periodic checkup (like we have for aircraft) is unaffected; this will for sure include any position reporting element, but by far not being limited to. Even this can be done nearly free of charge for the user, since the performance of position reporting equipment can be verified by ground MLAT systems and automatically fed into a database.


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Fixed ground equipment around airports will have OPEX costs as other surveillance receivers do. Collocate the UAS ADS-B receivers with existing surveillance receivers (which makes sense also in terms of network, maintenance, facility etc.) reduces that to a minimum. It is likely, that UAS ADS-B might be integrated into commercial ADS-B receivers for surveillance.

The provision and broadcast of Geofencing data requires OPEX by the authorities. However they are already responsible to provide this information into a database. Due to the criticality of such data and the importance of adherence to those regions, it should be made as easy as possible for air space users to gather this information. Public authorities should opt to spend money better in open and easy dissemination of this information instead of establishing a complicated enforcement system to monitor if everybody has downloaded the most recent database.

5.3. TECHNOLOGICAL MATURITY

The solution is technologically mature insofar, that required chipsets, waveforms, receivers etc. are available; there is no technical implementation risk. For a full system, custom PCBs need to be designed and for large quantities, design of specific ASICs is required to reach the final price target. However this is usual in industry and generates a valid business case for hardware manufacturers once the outline of the specification is available.

The following sections show solutions, which are close to what we propose and which are fully representative in terms of size, weight, power and performance (but use slightly different frequency or protocol, do not have formal authorization etc.)

For E-Identification, a small box like the Ping ADS-B receiver is good candidate at the low weight end (requiring a different frequency and protocol).

The datasheet clearly states, that within this weight envelope already a transmission capability is possible; it uses a dedicated IC containing all relevant processing. It also is capable of multi frequency reception, therefore a notional combination with Detect-and-Avoid function would not significantly add significant weight nor power consumption.

FLARM uses LoRa waveforms, which could be a candidate for E-Identification also. Such chipsets are already available with very small size and weight, e.g. here (FANET+ / Skytraxx):


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Typical properties are: Tx power up to 100 mW CW, link budget of 157 dB (all losses between Tx and Rx; path loss typically up to 140 dB), 12 mW Rx current, 120 mA Tx current (@ 1% duty cycle). Form factor is 15*25*4 mm; It needs a position source (GNSS chip) and a Processor to operate (which could be integrated on that PCB as well). For 1090 MHz auto avoid functionality, a separate 1090 MHz receiver is required, but is already available as single chip solution.

The geofencing solution can be directly demonstrated with existing devices; candidates for the ground beacons were the LPAT devices developed by funke19.

5.4. TIMELINE FOR MARKET ENTRY

Demonstration systems are available almost immediately, since ultimate optimization for lowest weight is not required here. A custom made PCB using already available hardware could be available below 30g for the lowest performing class – including ADS-B and drone UAS. For further optimization, a mixed signal ASIC could be considered combining ADS-B reception and the UAS ADS-B transceiver functionality at lower size, weight, power and prices than the currently available solutions. Target weight of below 10g should be possible for the lowest performance class.

Commercial products could be available fast; the limiting time is here not the commercial development but more the regulatory framework which needs to be established until commercial entities are willing to invest e.g. into custom chip fabrication. There are no technological nor implementation risks, since the environment and technology is well-known.

The geofencing beacons are technically existing, however a protocol needs to be defined, either using reserved DF18 frames or unused other DF. The system can be set in place for UAS relatively small, since their onboard systems usually have S/W update capability. For the remaining users like G/A, the additional information needs to be received, processed and visualized, which is not the case in current avionics; but many aircraft in this segment are not equipped with ADS-B out and also not with ADS-B in. However this add-on function could be a motivation to GA pilots and owners to reconsider an ADS-B In/Out installation in their craft, since then this technology delivers immediate benefit rather than producing purchase, installation and maintenance costs only. The notional timeline will mainly be driven by the availability of standards and equipment availability in the 2023 range. Demonstration can be done right away.

19 See http://www.funkeavionics.de/45.html?&L=1.

http://www.funkeavionics.de/45.html?&L=1


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ANNEX A TECHNICAL DISCUSSIONS

Annex A-1. WAVEFORM

The waveform for the proposed UAS-ADS-B can be freely chosen, since it is a new design. Therefore we can design a waveform suitable for a large number of participants receivable in robust environment. The detailed design shall be left to a dedicate study, however the following requirements can be identified:

Implement some method of FEC

Trade-off burst length to required pulse power (very high pulse power is usually much more difficult compared to lower power and longer bursts).

Use lower bit rate on the bursts.

Trade lower bandwidth in FDMA or CDMA; CDMA could have advantages when less users are present in the channel.

Consider hybrid modulation at least in some messages (spread spectrum with different bit rates on same signal) allowing reception of core information with lower S/N than reception of detailed information.

There are already robust waveforms in place, especially in the M2M or IoT domain, which could be considered as candidates, e.g. LoRaWAN20. Especially when coexisting with some existing signals, spread spectrum modulation produces advantages and the mutual interference is very low. This would – for example – create a possibility for limited coexistence between UAS ADS-B and DME (which need to be verified in a detailed study).

Annex A-2. MEDIA ACCESS

The ADS-B on 1090 MHz was primarily based on a combination of two message types:

Interrogation based signals with a defined processing time, used by SSR primarily for ranging applications. The data payload of Mode-S is an “add-on” to the ranging functions.

Broadcast signals randomly transmitted “between” the radar replies.

Since we will use a dedicated frequency, the media access can be newly defined.

Annex A-2.1 Known transmission time:

Here, the useful feature of one-way ranging should be implemented, which adds almost no resource penalty, but allows one-way ranging as verification.

To achieve this, a defined transmission time is required. In analogue designs this is a complicated function, however for digital based transmitters, a transmission to a predefined time is feasible. Any craft having a GPS onboard is able to keep its internal time to something around 30 to 100 ns within true GPS time, therefore this accuracy of transmission time is possible. 100 ns correspond to a signal travelling distance of 30 m.

20 See https://www.lora-alliance.org/what-is-lora, hardware developer is www.semetech.com, retrieved 11/2017. FLARM uses LoRa chipsets (e.g. SX1272) – see https://github.com/3s1d/fanet-stm32/blob/master/fanet_module.pdf.

https://www.lora-alliance.org/what-is-lora

http://www.semetech.com/

https://github.com/3s1d/fanet-stm32/blob/master/fanet_module.pdf


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Annex A-2.2 (Modified) Self-organized TDMA:

Similar to maritime AIS, a more coordinated media access shall be foreseen. For very simplistic communication and as a fallback option, a full TDMA implementation might not be possible on the “simplest” services, however it should be noted that the Aloha access limits considerably the channel capacity as we have seen on classic ADS-B.

When the craft is aware of current UTC time – this is the case once it is able to determine its position using GNSS – a more elaborated method should be used. SOTDMA alone increases the efficiency the channel is used. However, AIS and ADS-B have a systematic drawback – the packet content (i.e. the position data) is determined locally onboard the craft and is trusted in all following applications, since it is quite difficult to verify if the position data is correct. Therefore, a TDMA like access scheme is envisaged together with the feature of a known transmission time. In order to minimize simultaneous conflicting transmissions, the following strategy is proposed:

Use a part of the UAS ID to identify “valid” transmission slots (some hash function).

There should be several 100 valid transmission slots per second, a given UAS should be able to use one to two per second for transmission of its position. Within a given second, we have around 100 independent slots.

The valid slots should vary in a pseudo-random way using the UAS ID so that in every second (“reporting interval”) other IDs share one transmission slot. UAS which produce simultaneous transmissions in reporting interval n should be separated in reporting interval (n+1).

Using a spread spectrum waveform (like LoRaWAN) could be used to transmit simultaneously using different spreading codes. This increases further the number of possible objects within an area and facilitates degarbling.

Furthermore, some slight frequency diversity could be used. Especially for the “better equipped” larger craft, frequency tolerances can be relatively tight today – having GNSS reception allows immediately to measure21 the own reference frequency to 10-7 to 10-8, translating to some 100 Hz for carriers in the L to C band range. Frequency tolerances of single kHz will be no technical challenge.

Guard times should be minimized to utilize the channel capacity in a maximum way. This will – especially for long range reception -. Produce some colliding messages; however due to spread spectrum codes, frequency diversity and a pseudo-random slot allocation the degradation is gracefully. Furthermore, the closest target is still receivable, important for all services requiring information within proximity only.

Annex A-2.3 Spread Spectrum Access:

A combination between TDMA and CDMA could present advantages. The TDMA component allows the implementation of a defined well-known transmission time allowing one-way ranging verification whereas CDMA allows producing signals with improved robustness to CW and narrow band interferers. For reception by satellites, where collisions on the frequency may exist, this enables a better degarbling implementation as we have now on ADS-B.

Long range services may also use hybrid modulation techniques, offering a low bitrate content receivable with lower S/N (and even receivable by satellites) overlaid by a high bitrate content carrying additional

21 COTS GPS receivers produce single shot PPS accuracies of better than 100 ns, typically in 10’s of ns. Short term stability (10 seconds range) of crystal oscillators are easily in the 10-8 range.


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information, but requiring higher S/N. There are various techniques already known, so that details are left to a specialized study.

Annex A-3. FREQUENCY / CHANNELS

Annex A-3.1 Services and Channels

Different operation classes of UAS could use separate (but adjacent) channels. A SDR receiver is possible to process the whole frequency band instantaneously, therefore the distribution to multiple channels will not produce a technical constraint.

Low performing craft could use a very simplistic channel access, having the potential of producing multiple collisions. Such craft would be visible only from near range, while from far away too many overlaps prevent a system from receiving the targets. Since such UAS are usually low and slow, a far range capability is not required.

High performing craft are much less in number, and can maintain the media access more properly. They will stay in their assigned slots, produce a well-defined ensemble thus allowing a far range reception. The “best” UAS class could then even allow a satellite based reception. Consequently, their allowed density is lower than for “toy craft”, however one should consider that still the density is much higher than for aircraft.

For example (channel can mean one frequency plus several DSSS codes or several subfrequencies):

Channel 1: Channel dedicated for smallest systems (open category), uncontrolled Aloha access; short frames containing position (if any), ID and basic status only. Frame length max. 1 ms, intended range few nm only. This channel will be used by most of the small craft.

Channel 2: Channel dedicated for small systems (open category), SOTDMA like coordinated access to maximize channel capacity. Limited to craft being aware of time and position (if not, stay in channel 1 until the information becomes available). Limited output power and intended reception range 10 nm only. Small craft (expected in the MTOW between 2kg and 5 kg) should use this channel.

Channel 3: Similar to channel 2, but for specific category only. Intended reception range up to some 20 nm. This would be used for craft operating VLOS and under direct operator control. There is no need to detect them using satellites; in all areas where their position needs to be known, sufficient terrestrial receivers will be used. SOTDMA, but transmission timestamp not known to below several 100 µs. Independent position verification needs TDOA systems with at least three receivers.

Channel 4: Medium range channel, for specific category only. SOTDMA with defined transmission time (100 - 300 ns knowledge) randomly hashed by craft ID. Adds one-way ranging capability (in the order of 100 m) to the messages. Intended reception range (free space) up to 30 .. 50 nm, comparable to 10W ADS-B transmitter (scaled with waveform). Probably satellite reception possible under ideal conditions in second step of the system. Independent terrestrial position determination needs TOA measurement with at least two receivers. It is expected that this channel is used mostly by craft around 25 kg operating regionally BVLOS but not going too remote (e.g. wind farm monitoring, regional delivery [some km]).

Channel 5: Long range channel, intended for satellite reception, specific category only. Defined transmission time, more stringent than channel 4 (e.g. 50 to 100 ns knowledge), which adds one-way ranging to below 50 m. Output power comparable to aircraft class A0 transponder (scaled with waveform). Satellite reception possible under real conditions encountered in low to medium density airspace (North Europe, Russia, Canada, Alaska, Central US, …).


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It is expected, that this cannel is used mainly by craft in the 25kg to 150 kg level (except when operating in the certified category) operating BVLOS / BRLOS with considerable autonomous activity.

Channel 6/7: This channel pair should be reserved for UAS to UAS communication in case any deconflicting function is used (like TCAS / ACAS). Relevant for specific category only; not expected to be implemented in open category. One channel is a dedicated “interrogation” frequency for those craft capable of, the other is to broadcast the details of the planned deconflicting measure. If this results into an action, the intent is then transmitted also in the appropriate channel (1 to 5). This channel pair is intended for short to medium range only (scaled by the UAS speed capability), but usually below 10 nm. This channel pair might be received by ground based receivers – mainly for conformity monitoring. There is no need for satellite reception.

The communication can also be adaptive (e.g. using long range communication in more remote areas). The selection process will be cognitive and does not require user interactions.

Annex A-3.2 Potential Frequencies

Potential frequencies require a thorough search, the information given here shall just provide an overview of potential candidates; the list is not intended to be complete.


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ANNEX B POTENTIAL SATELLITE SYSTEM

Like on “classic” ADS-B, also reception via satellite is possible for the “heavier” systems. Since they may operate in VLL in remote areas, they might be beyond the range of a terrestrial network. Even mobile networks may lack coverage there.

Since they are always broadcasting the information, everyone in vicinity gets aware of this airspace user and ATC (or a UTM service provider) can get surveillance information; in absence of terrestrial receivers by using a satellite system.

ADS-B satellite reception has shown that this system works for several 1000 participants in view. On UAS, the situation is even better since here a frequency is used free from legacy present on 1090 MHz22. Capacities of ten thousand craft within one (satellite) receiver channel / ground footprint is possible and should allow the accommodation of UAS at least for the near future.

In case the system should be saturated, the initial design should allow for additional channels; due to the SDR nature of any technology this should not produce a severe constraint.

Annex B-1. CONSTELLATION

Currently many proposals of LEO constellations are raised. The proposed system would need a lightweight payload onboard the satellites only, which could be a rideshare partner of many ADS-B, AIS or IoT missions.

From the link budget or mission type, the proposed service is very similar to IoT or M2M services, especially:

The emitters are light (grams) and should not consume significant power (like battery powered tags). EIRP is in the order of single watts for single ms bursts.

The emitters travel worldwide and are operated worldwide, preferably without the need of prior setup or country-specific authorisation.

Usually, hundreds to several thousand emitters are in simultaneous view of the satellite.

The emitters do not actively coordinate their media access on a global basis and there is no global media access control. There might be a SO-TDMA mechanism, but limited to a “bubble”, which is not effectively preventing collisions from a satellite’s point of view.

The data rate is quite low (assuming 1 message per second of 20 bytes we are on the order of 1 kByte/minute or 60 kByte/hour. The reception “yield” on the satellite should be in the order of 20 to 50%. This is well within the data rates expected by IoT and M2M missions.

Several IoT constellations would be able to carry such a payload.

Annex B-2. SATELLITES

The envisaged satellites and payloads are optimum for small to microsat applications. Demonstrators could even have cubesat size.

22 One should note that on 1090 MHz – especially in medium to high density airspace – the majority of transmissions is not ADS-B, but reply to other interrogations such as TCAS or SSR. Once free to design waveforms and channel access, the capacity of one reporting channel can be considerably increased – a factor of 10 is easily possible.


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Annex B-3. GROUND INFRASTRUCTURE

The ground infrastructure needs to distribute the data in near real-.time. The satellite access is not used for real-time deconflicting of air traffic (this is done by listening to the locally emitted signals), any situational awareness should get the data within one minute maximum. Therefore, store-and-forward is not possible (except for proof-of-concept applications).

However this mission profile is quite similar to IoT and M2M missions.


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ANNEX C TECHNICAL DATA SHEETS

This annex contains a collection of data sheets of products cited in the White Paper. It is intended for technical orientation only (to show what can be bought right now) and does not endorse any pre-selection of technology nor is any indication of preferred technology.

It shall also be noted that the selected items are not implementing the proposed service; they implement something which is comparable and “technically” identical (in terms of size, weight, integration logic, radio performance, link, antenna etc.). Clearly, equipment fully matching the proposed service needs to be carefully re-evaluated and selected.

It shall also be noted that the proposed service consists of several elements (detect and avoid, ID report, position report, mutual auto avoid, geofencing) which have today separate equipment candidates. Once defined, industry will merge the relevant components together which gives a considerable advantage over single components (a prominent example is a smartphone, which combines also various technologies in an efficient way).

Annex C-1. EXISTING EQUIPMENT

Annex C-1.1 Detect and Avoid (1090 MHz)

The smallest available pingRX23 would be sufficient for the smallest category of UAS delivering already a comprehensive data set requiring only very low resources (size, weight, power): (http://uavionix.com/downloads/integration/uAvionix%20Ping%20Integration%20Guide.pdf.)

For the proposed system, the details need to be refined, but the overall technical envelope proves that such a system is feasible already for very light objects with not lots of power. Such a box could for example, easily be integrated in UAS of 2 kg MTOW and above without noticeably decreasing it useful weight, range, endurance or other performance. By using a worldwide standard, it receives already every current ADS-B equipped aircraft and if will receive also any future equipped G/A aircraft “wishing” to be seen by UAS.

23 Source: http://uavionix.com/downloads/pingrx/docs/uAvionix-pingrx-data-sheet-ap0.pdf, retrieved 11/2017

http://uavionix.com/downloads/integration/uAvionix%20Ping%20Integration%20Guide.pdf

http://uavionix.com/downloads/pingrx/docs/uAvionix-pingrx-data-sheet-ap0.pdf


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Figure 5-1: Short datasheet of PingRX (smallest member of family)


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Figure 5-2: PingRX Integration guide – data content

Especially the second record set contains the data the UAV is collecting about its own position and therefore a good candidate for a UAS position reporting telegram. The datasheet already indicates ADS-B out transmission capability (enabled due to regulatory reasons).

Annex C-1.2 Full blown transponder

The device presented here will be suitable for the certified categories for UAS (usually close to 150 kg MTOW), which exceeds the scope of this White Paper. However it demonstrates that even full blown transponders which functions exceeding what is proposed here, can be realized with minimum size, weight and power. Even for a craft of 25 kg MTOW, this transponder is technically feasible (what we propose will then be definitely smaller).


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Figure 5-3: Ping 200Si (certified) UAS transponder

Annex C-2. CANDIDATE TECHNOLOGIES

Technologies cited here shall demonstrate, that some solutions are available without long term development needs. The selection does not endorse a specific solution nor it is any preselection.


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Annex C-2.1 Semetech SR1272

The following chip24 is a single chip modem employing the required elements for a potential L-Band demonstrator. It could readily be used to demonstrate such a function in the 960 to 970 MHz range without modification. Similar platforms are used in FLARM.

Figure 5-4: Semtech SX1272 block diagram (LoRa single chip solution)

The output power of 100 mW would be sufficient for demonstrations up to some nm range. For more robust applications including satellite reception, an additional PA would be required (e.g. LDMOS for up to 10W).

LoRa chips are built for stand-alone operation not requiring any ground infrastructure, which needs to be established in parallel. However operation on ISM should definitely be avoided since this locks the operation to a specific area avoiding easy transportation.

Annex C-2.2 Sigfox

Sigfox is in principle showing a potential solution in terms of signal design by demonstrating long range connections with low power transmissions. Various low power chips are readily available (e.g. M2C800125)

On the first glance, such an implementation looks promising, since the infrastructure is already in place. Just by equipping the objects with a simple chip a system is already working within a short period of time.

24 Full datasheet available at http://www.semtech.com/images/datasheet/sx1272.pdf. 25 Source: file:///D:/Users/T0101763/Downloads/M2C1101%20Rev%201.0%20-%20Uplynx%20M2C8001%20Product%20Brief.pdf.

http://www.semtech.com/images/datasheet/sx1272.pdf


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Figure 5-5: Sigfox coverage in central Europe (blue = covered, magenta = not covered). Source: Sigfox.com

However it also shows directly the drawback of operating in ISM networks by depending on local regulations, local frequency assignments and locally available ground stations. Therefore, such kind of solution may not work for equipment travelling around (e.g. US tourist operating his drone in Europe). The resulting coverage would be nevertheless patchy. When no ground infrastructure is in place, also functions like auto-avoid and position broadcast would not be possible, which is definitely not a desirable solution.

Therefore, low-power solutions are definitely feasible, but proprietary ground-based implementations definitely should be avoided.


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END OF DOCUMENT

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