Link Availability for LEO Constellations

Nicholas “Donnie” Laughton { BSc, BEng, MASc }

Technical Lead, Network OS and Virtualization

Advanced Systems Engineering Group

2018-04-05 www.telesat.com 1

2018-04-05 www.telesat.com 2

Outline • Introduction and Outline• Telesat GEO Satellites

• Static Link Analysis• Atmospheric Fading and Link Availability• Adaptive Mechanisms

• Telesat LEO Constellation• Dynamic Link Analysis• Atmospheric Fading and Link Availability in LEO• Adaptive Mechanisms in LEO

• Q & A

2018-04-05 www.telesat.com 3

Introduction • About Telesat• Established in 1969• 4th largest satellite operator in the world• Corporate headquarters in Ottawa

• Launched the first commercial domestic communications satellite in geostationary orbit – Anik A1

• Launched first commercial Ku-band satellite offering first direct-to-home (DTH) television service

• First satellite operator to provide Internet access to ISPs over satellite

• Several open positions for new grads

2018-04-05 www.telesat.com 4

Introduction • About Me• Academic Background

• Bachelor of Science, Molecular Genetics and Cellular Biology• Queen’s University (2009)

• Bachelor of Engineering, Aerospace Electronics• Carleton University (2013)

• Masters of Applied Science, Electrical Engineering• Carleton University (2017)• Thesis Topic: A Fully Integrated Distributed Active Transformer Power

Amplifier with Injection Locking• Professional Background

• Payload Design Engineer, MDA• Communication Systems Engineer, Telesat Advanced Systems

Engineering Group• Current Position

• Technical Lead, Network Operating Systems and Virtualization, Telesat LEO Program

2018-04-05 www.telesat.com 5

Telesat GEO Satellites

2018-04-05 www.telesat.com 6

Telesat GEO Satellites

2018-04-05 www.telesat.com 7

Static Link Analysis

2018-04-05 www.telesat.com 8

Static Link Analysis

Gateway Remotes

Uplink

Downlinks

2018-04-05 www.telesat.com 9

Static Link Analysis

2018-04-05 www.telesat.com 10

Static Link Analysis

IF IF

Gateway Remotes

2018-04-05 www.telesat.com 11

Static Link Analysis

IF IF

2018-04-05 www.telesat.com 12

Static Link Analysis

IF IF

Uplink Downlink

2018-04-05 www.telesat.com 13

Static Link Analysis

IF IF

EIRP G/TLosses EIRP G/TLosses

Uplink Downlink

𝐶𝐶𝑁𝑁 𝑈𝑈

= 𝐸𝐸𝐸𝐸𝐸𝐸𝑃𝑃𝑈𝑈 +𝐺𝐺𝑇𝑇 𝑈𝑈

− 𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝑈𝑈 − 𝑘𝑘 − 𝐵𝐵𝐶𝐶𝑁𝑁 𝐷𝐷

= 𝐸𝐸𝐸𝐸𝐸𝐸𝑃𝑃𝐷𝐷 +𝐺𝐺𝑇𝑇 𝐷𝐷

− 𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐷𝐷 − 𝑘𝑘 − 𝐵𝐵

𝐶𝐶𝑁𝑁 𝑇𝑇

−1

=𝐶𝐶𝑁𝑁 𝑈𝑈

−1

+𝐶𝐶𝑁𝑁 𝐷𝐷

−1

margin

2018-04-05 www.telesat.com 14

Atmospheric Fading and Link Availability IF

EIRP G/TLosses

• Path Loss is due to physical distance• Atmospheric Loss is due to environment

2018-04-05 www.telesat.com 15

Atmospheric Fading and Link Availability

The propagation loss on an Earth-space path, relative to the free-space loss, is the sum of different contributions as follows: – attenuation by atmospheric gases; – attenuation by rain, other precipitation and clouds; – focusing and defocusing; – decrease in antenna gain due to wave-front incoherence; – scintillation and multipath effects; – attenuation by sand and dust storms.

Each of these contributions has its own characteristics as a function of frequency, geographic location and elevation angle. As a rule, at elevation angles above 10°, only gaseous attenuation, rain and cloud attenuation and possibly scintillation will be significant, depending on propagation conditions.”

2018-04-05 www.telesat.com 16

Atmospheric Fading and Link Availability

𝐶𝐶𝑁𝑁 𝑈𝑈

= 𝐸𝐸𝐸𝐸𝐸𝐸𝑃𝑃𝑈𝑈 +𝐺𝐺𝑇𝑇 𝑈𝑈

− 𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝑈𝑈 − k − B

• Free Space Path Loss• Gaseous Attenuation• Rain and Cloud Attenuation• Scintillation

exceedance

e.g. “Link is available 99.5%”

2018-04-05 www.telesat.com 17

Adaptive Mechanisms

• Uplink Power Control• Linearity• $$$

𝐶𝐶𝑁𝑁 𝑈𝑈

= 𝐸𝐸𝐸𝐸𝐸𝐸𝑃𝑃𝑈𝑈 +𝐺𝐺𝑇𝑇 𝑈𝑈

− 𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝑈𝑈 − 𝑘𝑘 − 𝐵𝐵

2018-04-05 www.telesat.com 18

Adaptive Mechanisms

• Adaptive Coding and Modulation• Throughput• Margin

𝐶𝐶𝑁𝑁 𝑈𝑈

= 𝐸𝐸𝐸𝐸𝐸𝐸𝑃𝑃𝑈𝑈 +𝐺𝐺𝑇𝑇 𝑈𝑈

− 𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝑈𝑈 − 𝑘𝑘 − 𝐵𝐵

2018-04-05 www.telesat.com 19

Adaptive Mechanisms

• Adaptive Bandwidth Allocation• Throughput• Modem Complexity

𝐶𝐶𝑁𝑁 𝑈𝑈

= 𝐸𝐸𝐸𝐸𝐸𝐸𝑃𝑃𝑈𝑈 +𝐺𝐺𝑇𝑇 𝑈𝑈

− 𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝑈𝑈 − 𝑘𝑘 − 𝐵𝐵

2018-04-05 www.telesat.com 20

TelesatLEO Constellation

2018-04-05 www.telesat.com 21

TelesatLEO Constellation

Phased Array Antennas

Optical Intersatelite

Links

Regenerative Payload

Software-Defined Network

2018-04-05 www.telesat.com 22

TelesatLEO Constellation

• Phased Array Antennas Phased Array Antennas

Optical Intersatellite

Links

Regenerative Payload

Software-Defined Network

Source: Wikipedia

Digital Beam Forming

AnalogBeam Forming

Beam

For

min

g N

etw

ork

Beam

For

min

g N

etw

ork

2018-04-05 www.telesat.com 23

TelesatLEO Constellation

Phased Array Antenna

Optical Intersatellite

Links

Regenerative Payload

Software-Defined Network

• Optical Inter-satellite Links

2018-04-05 www.telesat.com 24

TelesatLEO Constellation

• Regenerative Payload Phased Array Antenna

Optical Intersatellite

Links

Regenerative Payload

Software-Defined Network

OBP

𝐶𝐶𝑁𝑁 𝑇𝑇

−1

=𝐶𝐶𝑁𝑁 𝑈𝑈

−1

+𝐶𝐶𝑁𝑁 𝐷𝐷

−1

2018-04-05 www.telesat.com 25

TelesatLEO Constellation

• Software Defined Network Phased Array Antenna

Optical Intersatellite

Links

Regenerative Payload

Software-Defined Network

Source: Metro Ethernet Forum

2018-04-05 www.telesat.com 26

Dynamic Link Analysis

IF IF

EIRP G/T EIRP G/T

2018-04-05 www.telesat.com 27

Dynamic Link Analysis

IF IF

EIRP G/T EIRP G/T

IF IF

EIRP G/T EIRP G/T

IF IF

EIRP G/T EIRP G/T

IF IF

EIRP G/T EIRP G/T

2018-04-05 www.telesat.com 28

Dynamic Link Analysis

𝐶𝐶𝑁𝑁 𝑈𝑈

= 𝐸𝐸𝐸𝐸𝐸𝐸𝑃𝑃𝑈𝑈 +𝐺𝐺𝑇𝑇 𝑈𝑈

− 𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝑈𝑈 − 𝑘𝑘 − 𝐵𝐵

𝐶𝐶𝑁𝑁 𝑈𝑈

𝑡𝑡 = 𝐸𝐸𝐸𝐸𝐸𝐸𝑃𝑃𝑈𝑈 𝑡𝑡 +𝐺𝐺𝑇𝑇 𝑈𝑈

𝑡𝑡 − 𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝑈𝑈 𝑡𝑡 − 𝑘𝑘 − 𝐵𝐵

Terminal Phased Array Satellite Phased Array

Dynamic Geometry

2018-04-05 www.telesat.com 29

Atmospheric Fading and Link Availability in LEO

• Solving the dynamic fade likelihood

exceedancex

𝑝𝑝 𝐹𝐹𝐹𝐹𝐹𝐹𝐿𝐿 < 𝑥𝑥 = �𝜃𝜃=0

90

𝑝𝑝 𝐹𝐹𝐹𝐹𝐹𝐹𝐿𝐿 𝜃𝜃 < 𝑥𝑥 × 𝑝𝑝 𝜃𝜃

2018-04-05 www.telesat.com 30

Adaptive Mechanisms in LEO

• Same as GEO• Diversity (pick a better link)• Adapting the satellite

• Beam Zooming (improve G/T and EIRP)• Downlink Power Control (power pool from phased array)

2018-04-05 www.telesat.com 31

• Questions?