1. UAS BLOS (satellite) Control and Non-Payload (CNPC) Communications
Michael Neale
Brooks Cressman
Hau Ho
ICAO ACP WG-F/24
March 21, 2011

2. Agenda UAS SWAP Limitations
UAS Throughput and BLOS Spectrum Requirements (RTCA)
Spot Beam Satellite Technology and impact on spectrum
BLOS Candidate Frequency Bands (ITU WP 5B Study)
Study Summary – Advantages and Disadvantages
Ku/Ka FSS (Fixed-Satellite Service) Systems Performance
System Link Availabilities / Rain Fade calculations
Study Summary
UAS SWAP Limitations
Example installations
Operational Interference Environment
Conclusions

3. Data Rate and Spectrum Requirements
Required Throughput (RTCA & ITU)
Telecommand: 10 kbps
Telemetry: 320 kbps
UA Densities (RTCA)
1856 UA in regional beam (3M mi2)
501 UA per spot beam (486 mi diameter footprint)
Spectrum requirements (M.2171)
169 MHz
1 satellite using global/regional beam
Small UA not supported
56 MHz (169/3)
≥ 3 satellites using regional beams
UA uses directional antenna
46 MHz*
≥ 3 satellites using spot beams
The satellites can operate co-frequency if the UA uses a directional (high gain) antenna with sufficient off-axis performance
The satellites cannot operate co-frequency if the UA has an Omni directional (low-gain) antenna due to interference

4. Spot Beam Satellite Technology
Used on existing & planned 20/30 GHz band satellites
Relies on tens/hundreds of beams to achieve high Power Flux Density (pfd) and spectrum efficiency levels
Spot beams allow spectrum to be re-used across service area
Typical scheme is 4x frequency re-use to achieve their required space isolation (see below). For UAS this means a minimum of 4x46 MHz is needed, but in reality each beam will have 125 or more MHz of spectrum to serve many applications.
Typical 20/30 GHz satellite 3 dB “spot” beamwidths
0.5º (~310 km beam diameter/nadir)
1.0º (630 km beam diameter/nadir).

5. Potential BLOS Frequency Bands Studied in WP5B
MHz
AMS(R)S allocation
20 MHz spectrum in each direction
Currently no satellite on orbit
12/14 GHz also known as “Ku-band” satellites
FSS allocation
>200 geostationary orbit satellites (GSO) currently on orbit
500 MHz (1 polarization) – 1000 MHz (dual pol.) in each direction
20/30 GHz also known as “Ka-band” satellites
FSS allocations
>10 Commercial FSS GSO satellites are currently on orbit
Several proposed systems will be on orbit in the next few years
1000 MHz – 2000 MHz spectrum in each direction
13/15 GHz & 23/24 GHz
AMS(R)S allocations
Unable to share with other services (ITU WP5B studies)

6. L-band AMS(R)S Overview (RTCA)
Type of Allocation
UA Terminal Antenna
Study Summary
Disadvantages/
Potential Issues
Advantages
10 MHz of the & MHz MSS Allocation
GSO satellites
AMS(R)S Allocation
Low-Gain antenna (Omni)
Can support UAS control links
Link availability needs further study
Spectrum limitation
One satellite per region
Shared with MSS systems
Operate in AMS(R)S allocation
Satellites on orbit
Global coverage
MHz
NGSO - MSS satellites
Two NGSO MSS in this band
Spectrum limitation - only 4 MHz in each direction (HIBLEO 2)
L-Band spectrum not sufficient for all projected UAS Requirements

7. Above 5 GHz Study Summary – Advantages & Disadvantages
Band
Study summary
Disadvantages
Advantages
5 GHz bands
May be able to support UAS control links (BLOS)
Sharing difficulties (MLS)
No satellite on orbit
Only ~5 MHz per spot beam and1 satellite per region greatly constrains spectrum
Operate in ARNS allocation
UA operates with omni antenna
12/14 GHz bands -- commercial satcom
Support UAS control Links
Meet the UAS system link availability
Operate in FSS allocation, not AMSRS
100’s of satellites on orbit
Global coverage
Used for decades to provide BLOS service to UAS
> 500 MHz in each direction
13/15 GHz bands
Can’t share with the existing and planned systems in these bands
Unacceptable interference to passive sensors in adjacent bands
Spectrum limitation
22/23 GHz bands
20/30 GHz bands – commercial satcom
Support UAS control links
Allocated to the FSS and, in some bands, the MSS. No specific AMS(R)S allocation.
Several satellites on orbit
Many more planned
> 1000 MHz in each direction
Service UAV using small antenna

8. Ku & Ka band System Study Summary (Based on ITU-R WP 5B)
Ku and Ka-band satellite systems can support UAS control links and meet the system link availability
Ka-band appears more suitable than Ku-band because it allows UA to operate with smaller antennas
Ka-band is more impacted by rain than Ku, but still achieves higher link availability
Ka-band operates at higher pfd and Uplink EIRP density
To meet the safety levels, the UA control link availability is ~ %
UA will be equipped with more than one control link. If UA has two control link subsystems, each link only required to achieve 99.8%
CS (control station): 99.95%
UA: 99.85%
ITU-R WP 3M, 4A, 4B are currently reviewing WP5Bs analysis.

9. Ku & Ka band System Availability
Ku-band
Ka-band
Ku-band- Telemetry link - 20º E.L.
Ka-band- Telemetry link - 20º E.L.
Ku-band- Telecommand link - 20º E.L.
Ka-band- Telecommand link - 20º E.L.

10. Ka Band Link Margin Summary
Telecommand downlink (satellite-to-UA): If the UA operates with a 0.5 m antenna the system can achieve 6.7 dB rain fade margin.
Telemetry uplink (UA-to-satellite): If the UA operates with a 0.5 m antenna and a 10 W transmitter the system can achieve a 14.6 dB rain fade margin.
These rain fade margins would be adequate to achieve the desired link availability for most locations around the globe particularly when the UA is operating at altitudes higher than 1.5 km.

11. UAS SWAP Considerations
UA’s are size, weight & power (SWAP) limited
Satcom equipment (antenna) impacts airframe design / size
Large antenna, or multiple equipment requires larger airframe, increasing cost, complexity and limiting applications
Antenna solutions tied to system architecture and UA design
At lower frequencies, omni antenna on UAS is used with large G/T on satellite
Drawback is spectrum cannot be re-used and only 1 satellite can be used per region so more spectrum is required or UAS density is limited. Benefit is that antenna implementation is simple.
At higher frequencies, rain fade is pronounced and high gain antennas are used to reduce SWAP, offset losses and meet off-axis requirements
Examples : for a constant gain of 38 dB,
X band = 1.18 meter
Ku band = .86 m
Ka band = .47 m
Upper limit on frequency due to increasing rain fade, and availability of satellite infrastructure.
Ka band is a practical limit for rain fade (up to 14 db)
CNPC satcom must also carry payload sensor data for practical SWAP

12. 0.76m Ku Band installation

13. 1.2m Ku Band Installation Sensor data processor Sensors
Flight Computer
Sensors

14. FSS Operating Environment
FSS Coordination process
FSS operators use ITU API/Coordination/Notification/BIU Filing process
Examination by ITU triggers Coordinations based upon proximity (arc) or potential noise floor impact (ΔT/T). Operators can also separately request a Coordination if they find a ΔT/T exceedance
Operators coordinate operating parameters to meet performance requirements
ITU examines notices with respect to compliance with the Radio Regulations (RR)
ITU definitively records assignments with favorable findings with respect to compliance with RR, including completions of coordination
Assignment may be recorded if coordination is incomplete after 4 months of interference free operation
ICAO SARPS for UAS could require users to provide for backup spectrum for use in the event their channel was to receive interference
Aviation regulator will certify UAS operators based upon successfully meeting ICAO SARPS and national regulations

15. Conclusions (1/2)
ITU and RTCA studies indicate UAS requires 46 to 169 MHz of spectrum
SWAP requirements and practical satellite design drive UAS toward low gain omni or smaller directional antennas in Ka band
Resulting actual spectrum needs become 169, 184 MHz or more (500 MHz…)
Existing AMS(R)S allocations do not meet projected UAS needs
Additional spectrum is needed and FSS can be explored as a way to provide ready bandwidth, meet safety requirements, and support future UAS applications

16. Conclusion (2/2)
Call for additional studies in ICAO 1.3 background text
Currently: "Spectrum  for  UAS  for safety and regularity of flight, and in particular when  the UAS operates in civil airspace, needs to be accommodated under an allocation to  the  aeronautical  mobile (R) service, aeronautical mobile satellite (R) service,  or  the aeronautical radionavigation service in order to receive the sufficient status and protection from harmful interference.“
Add: “STUDIES ARE REQUIRED AND UNDERWAY TO DETERMINE IF OPERATION OF UA UNDER OTHER RADIO SERVICES CAN BE ACCOMMODATED WHILE SATISFYING THE NECESSARY ICAO TECHNICAL REQUIREMENTS.”