Presentation on theme: "Satellite connectivity"— Presentation transcript:
1 Satellite connectivity Skills: noneIT concepts: geostationary, medium-Earth, and low-Earth orbit satellite characteristics, spectrum and licensing, satellite technology progress, important Internet-service satellite projects and some of their implicationsThis work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 License.
2 Where does this topic fit? Internet conceptsApplicationsTechnology (communication)ImplicationsInternet skillsApplication developmentContent creation (images)
3 Low-Earth, medium Earth and geostationary satellite characteristics Altitude (miles)Latency (milliseconds)Orbit time (hours)LEO< 1,20020-25Around 2MEO1,200-22,236Around 12GSO22,23624Orbit characteristics calculatorWhy is the geostationary satellite altitude exactly 22,236 miles while LEO and MEO are ranges?Where would the moon fit in this picture?
4 Footprint of a proposed SpaceX Starlink satellite Starlink is the trade name of SpacX’s proposed Internet-service satellite constellation.All things being equal, will LEO, MEO or GSO satellites have the largest footprint?
5 Footprint example – LEO and VLEO The signal is strongest when the satellite is directly overhead and fades as it moves away. When it gets too weak, the ground terminal automatically switches to another satellite with a better signal.Where would the strongest signal would be within the footprint?
6 Geostationary orbit (GSO) 35,786 km (22,236 mi) and directly above the equatorVideo broadcast and slow InternetThe satellite remains over the same point on the Earth since it rotates around the Earth exactly once per day.Animate
7 Medium Earth Orbit (MEO) 1, ,236 milesGlobal Positioning System and medium speed InternetA relatively small constellation can insure full coverage of the Earth with multiple visible satellites. This animation shows the orbits of the GPS satellites and the number that are visible above the central US at a given time.AnimateSource
8 Low-Earth Orbit (LEO) Under 1,200 miles Earth imaging, science, fast Internet (?)To be sure the entire Earth is covered at all times, many more satellites are needed.This animation was prepared for Teledesic, which was formed in the 1990s, but failed because the technology was inadequate, Internet use was much less common and there was much less complementary terrestrial technology.Animate
9 Ku-band: 12 to 18 gigahertz GHz Ka-band: 26.5 to 40 GHz SpectrumKu-band: 12 to 18 gigahertz GHzKa-band: 26.5 to 40 GHzV-band: 40 to 75 GHzE-band: 60 to 90 GHzGood news – higher frequency means faster transmissionGood news – higher frequency means smaller antennasBad news – higher frequency means more power or less distanceBest news – you only have to know the previous good/bad news, not the frequency bandsThese statements are true given that other things remain equal. For example, more efficient
10 Licensed versus unlicensed spectrum Each country controls its own spectrum and the International Telecommunication Union tries to keep it uniform. The ITU is a UN agency.Did you apply to the FCC for a WiFi license? It WiFi is license-free.WiFi is in the 2.4 and 5 GHz bands.Do WiFi radios uses licensed or unlicensed spectrum?
11 Address the “digital divide” Do all Internet users have the same quality of service?Is there a digital divide within the United States?If successful, LEO will have many applications – the big one is to bring the Internet to unserved people.Source
12 Fewer, faster hops than fiber on long routes Another hoped-for advantageLos Angeles to Punta Arena, ChileSource
13 Teledesic failed in the late 1990s, what has changed?
14 In 1945, Arthur C. Clarke proposed geostationary satellite communication (The vision) “Fig. 2. Typical extra-terrestrial relay services. Transmission from A being relayed to point B and area C; transmission from D being relayed to whole hemisphere.”Extra Terrestrial Relays, Arthur C. Clark, Wireless World, October 1945, pagesClark is best known as a science fiction author. Check out the article on 2001 a Space Odyssey.Arthur C. Clark also wrote 2001 a Space Odyssey
15 Technology progress – ground station equipment The “dish” on the left could only establish a link to a satellite and it had to be precisely pointed at a geostationary satellite and transmission and latency were very slow.Today’s “terminal” includes the antenna and a fast computer for switching between satellites as they move and interfaces for the Internet, mobile phone network and Wifi. It will be simple for a user to install.Early geostationary satellite dish in rural IndiaProposed low-Earth orbit satellite terminal with solar panels
16 Technology progress – communication Beam formingHigh speedLaser between satellites
17 Technology progress – rocketry ReusabilityPayload increasesMilestonesFounded; 2002First Falcon 1 demo flight; 2006First Falcon 1 flight to orbit: 2008…First Falcon Heavy flight to orbit: 2018First BFR flight to orbit: 2022 (est)Payload to LEO (Falcon 1: 470 kg (expendable)Falcon 9: 13,150 kgFalcon Heavy : 33,800 kgBFR: 150,000 kgReuability of booster, second stage and fairingFalcon 1: ExpendableFalcon 9: Partial reuseFalcon Heave: Partial reuseBFR: Full reuseElon Musk says they would have gone bankrupt had the 2008 Falcon 1 flight failed – it was their fourth attempt.
18 SpaceX Starlink status Three leading contendersfour markets: Cloud service provider, mobile operators, air and sea, civil/governmentO3b mpower press conference:OneWeb statusSpaceX Starlink statusO3b status
20 SummaryWe have seen three types of satellite orbit – LEO, MEO and GEO – along with their characteristics, reviewed the technical progress that has made constellations of LEO and MEO Internet-service constellations possible and considered a few implications of their availability,
21 Track the progress of the Internet-service satellite projects here. ResourcesTrack the progress of the Internet-service satellite projects here.
22 Self-study questions I mentioned three leading companies Which one(s) is/are pursuing the consumer market?Which one(s) is/are pursuing other markets?What are some non-consumer markets for satellite connectivityWhich is best suited to the consumer Internet service market: LEO, MEO or GSO?Which has a larger footprint: LEO, MEO or GSO?Which has a longer latency time: LEO, MEO or GSO?What is latency a measure of?