6G: Connecting the Unconnected –

Non-Terrestrial Networks

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Marco Giordani, Mohamed-Slim Alouini, HaiboZhou, Yunfei Chen, Wei Feng, and Xiangling Li

CONNECTIVITY DIVIDE

World Wide BS Distribution

LTE (4G)

We are suffering from serious gaps in

global internet connectivity.

E. Yaacoub and M.-S. Alouini, “A Key 6G Challenge and Opportunity - Connecting the Base of the Pyramid: A Survey

on Rural Connectivity,” Proceedings of IEEE, April 2020. Available on arxiv.

GLOBAL CONNECTIVITY

HOLY GRAIL

“A telephone subscriber here may call up and talk to

any other subscriber on the Globe. An inexpensive

receiver, not bigger than a watch, will enable him to

listen anywhere, on land or sea, to a speech delivered

or music played in some other place, however distant.”

― Nikola Tesla 1919

Qu

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Cost per User in Remote Low Population Density Areas

Global Connectivity

Holy Grail Optic Fiber Cables

Microwave

Wireless Links

Classic

GEO Satellite

Low

High

High

Global Connectivity

Satellite Communication

UAV Communication

INTEGRATED SPACE-AIR-GROUND NETWORKS

Digital Divide: Rural Connectivity

Low Altitude Platform

Mega-Constellation

High Altitude Platform

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Backhaul

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Satellite Constellations Backhaul

Geostationary Earth Orbit (GEO) Satellite• Fixed position in the sky at ~35,000 km

• Relatively large delay

• ViaSat 1, 2, 3

Medium Earth Orbit (MEO) Satellite• 2,000~35,000 km

• Position and tracking

• O3B, SES Networks

Low Earth Orbit (LEO) Satellite• 160~2,000 km

• Hand-Over

• OneWeb, Starlink, TeleSat

LEO, Kuiper

Manufacturing Cost Down => Mass Production

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Hybrid VHT Satellite with Site Diversity

Conceptual Design for hybrid RF

(Ka band) and optical feeder

OGS

Weather

Conditions

OGS

RF service region

Site diversity to avoid the

atmospheric effect

RF GS

Satellite

RF GS

E. Zedini, A. Kammoun, and M. –S. Alouini, “Performance of multibeam very high throughput satellite systems based on FSO feeder links with HPA nonlinearity, IEEE Trans. On Wireless Communications, 2020

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Access

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Existing TV Infrastructure

• TV White Space (TVWS)

– Reusing TVWS unless harming TV channels

by interference

– VHF/UHF Band (i.e. 470~700 MHz )

– Ultra-wide coverage

TV Tower

M. Kishk, A.Bader, and M. –S. Alouini, “Capacity and coverage enhancement using long-endurancetethered airborne base stations” IEEE VT Magazine 2020

Tethered UAV/Balloon

Advantages• Unlimited flight time

• Supports heavier payload

• Wired/reliable backhaul link

• Mobility and relocation flexibility: Track the time-varying traffic

demand spatial distribution

• Line-of-sight with ground users: Probability increases with altitude

Tethered Balloons/Airships/Aerostats

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T. Staedter, “Soaring ‘Super Towers’ Aim to Bring Mobile Broadband to Rural Areas,” IEEE. Spectrum, April 2018.

B.E.Y. Belmekki and M.-S. Alouini, “Unleashing the Potential of Tethered Networked Flying Platforms: Prospects,

Challenges, and Applications,” Under review.

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High Altitude Platform (HAP)

balloon

Flight equipment

Mobile network provider

AQUILA

LOON

“Tower-in-the-air”• Solar-powered swarm of HAPs in the backbone network at

a height of 18-28 km

Y. Lee, K. -H. Park, Y. -C. Ko, and M. -S. Alouini, "A UAV-mounted free space optical communication: Trajectory optimization for flight time maximization", IEEE Transactions on Wireless Communications, Vol. 19, No. 3, pp. 1610-1621, March 2020.

Thank You ctl.kaust.edu.sa

Nikola Tesla(10 July 1856 – 7 January 1943)

“When wireless is perfectly applied, the whole earth will be converted into a huge brain, which in fact it is, all things being particles of a real and rhythmic whole. We shall be able to communicate with one another instantly, irrespective of distance.” Nikola Tesla (1925)