Wireless Communication and Networks

1. Wireless Communication and Networks Applications of Wireless Communication Wireless Communication Technologies Wireless Networking and Mobile IP Wireless Local Area Networks Student Presentations and Research Papers Satellite Communication and Networks http://web.uettaxila.edu.pk/CMS/AUT2012/teWCNms/

2. Communication Satellites • A Communication Satellite can be looked upon as a large microwave repeater • It contains several transponders which listens to some portion of spectrum, amplifies the incoming signal and broadcasts it in another frequency to avoid interference with incoming signals.

3. Motivation to use Satellites

4. Satellite Missions Source: Union of Concerned Scientists [www.ucsusa.org]

5. Satellite Microwave Transmission • Satellites can relay signals over a long distance • Geostationary Satellites • Remain above the equator at a height of about 22300 miles (geosynchronous orbits) • Travel around the earth in exactly the same time, the earth takes to rotate

6. Satellite System Elements

7. Space Segment • Satellite Launching Phase • Transfer Orbit Phase • Deployment • Operation • TT&C - Tracking Telemetry and Command Station • SSC - Satellite Control Center, a.k.a.: • OCC - Operations Control Center • SCF - Satellite Control Facility • Retirement Phase

8. Space Segment

9. Ground Segment • Collection of facilities, Users and Applications • Earth Station = Satellite Communication Station (Fixed or Mobile)

10. Satellite Uplink and Downlink • Downlink • The link from a satellite down to one or more ground stations or receivers • Uplink • The link from a ground station up to a satellite. • Some companies sell uplink and downlink services to • television stations, corporations, and to other telecommunication carriers. • A company can specialize in providing uplinks, downlinks, or both.

11. Satellite Uplink and Downlink

12. Satellite Communication Source: Cryptome [Cryptome.org] • When using a satellite for long distance communications, the satellite acts as a repeater. • An earth station transmits the signal up to the satellite (uplink), which in turn retransmits it to the receiving earth station (downlink). • Different frequencies are used for uplink/downlink.

13. Satellite Transmission Links • Earth stations Communicate by sending signals to the satellite on an uplink • The satellite then repeats those signals on a downlink • The broadcast nature of downlink makes it attractive for services such as the distribution of TV programs

14. Direct to User Services One way Service (Broadcasting) Two way Service (Communication)

15. Satellite Signals • Used to transmit signals and data over long distances • Weather forecasting • Television broadcasting • Internet communication • Global Positioning Systems

16. Satellite Transmission Bands The C band is the most frequently used. The Ka and Ku bands are reserved exclusively for satellite communication but are subject to rain attenuation

17. Types of Satellite Orbits • Based on the inclination, i, over the equatorial plane: • Equatorial Orbits above Earth’s equator (i=0°) • Polar Orbits pass over both poles (i=90°) • Other orbits called inclined orbits (0°<i<90°) • Based on Eccentricity • Circular with centre at the earth’s centre • Elliptical with one foci at earth’s centre

18. Types of Satellite based Networks • Based on the Satellite Altitude • GEO – Geostationary Orbits • 36000 Km = 22300 Miles, equatorial, High latency • MEO – Medium Earth Orbits • High bandwidth, High power, High latency • LEO – Low Earth Orbits • Low power, Low latency, More Satellites, Small Footprint • VSAT • Very Small Aperture Satellites • Private WANs

19. VSATs - Example of Customer Premises Earth station

20. VSATs • Home receiving systems for DTH service are also low in cost • The current generation of low-cost VSATs introduced since 2002 encourage greater use of bidirectional data communications via satellite. • As terminals have shrunk in size, satellites have grown in power and sophistication.

21. Commercial Satellites • There are three general classes of satellites used in commercial service, each designed for a particular mission and capital budget: • Smaller satellites • provide a basic number of transponders usually in a single frequency band. • Satellite operators in the United States, Canada, Indonesia, and China have established themselves in business through this class of satellites. • Measat satellite is example of this class • The introduction of mobile service in the LEO involves satellites of this class as well.

22. Commercial Satellites • Measat 1 provides service to Malaysia and throughout South East Asia

23. Commercial Satellites • Middle range satellites • Capable of operating in two frequency bands simultaneously. • AsiaSat 3C, provides 24 C-band and 24 Ku-band transponders to the Asia-Pacific market. • This increases capacity and decreases the cost per transponder. • Some satellites serve specialized markets such as GEO mobile satellites that connect directly with specially designed handheld phones. • An example of these satellites is Thuraya, using 12-m antennas.

24. AsiaSat 3C • A hybrid C/Ku band satellite with 48 Transponders

25. Thuraya 1 • Thuraya 1 provides high-power mobile satellite links to handheld terminals. (Courtesy of Boeing Satellite Systems.)

26. Commercial Satellites • Large Satellites • The trend to use the smallest possible DTH home receiving antenna and to cover the largest service area combine to demand the largest possible spacecraft. • The total payload power of such satellites reaches 15 kW, which is roughly 12 times that of Measat.

27. Commercial Satellites • While most of the money in satellite communications is derived from the broadcast feature, there are service possibilities where remote Earth stations must transmit information back to the hub Earth station. • Examples of such return link applications include: • Control signals to change the content of the information being broadcast (to achieve narrow casting on a broadcast link); • Requests for specific information or browsing of documents (to support Internet or intranet services); • Interactive services to update the record for a particular customer; • Point-to-point information that one remote user wishes to route to another remote user (like e-mail). • Adding the return link to the network tends to increase the cost of the remote Earth station by a significant amount since both a transmitter and controller are required. • Bandwidth on the forward and return links can be quantified for specific applications

28. Forward and Reverse Link Bandwidth • The approximate relationship of bandwidth usage between the forward link (hub transmit) and return link (remote transmit) in satellite applications.

29. Satellite Orbits Source: Federation of American Scientists [www.fas.org] • Geosynchronous Orbit (GEO): 36,000 km above Earth, includes commercial and military communications satellites, satellites providing early warning of ballistic missile launch. • Medium Earth Orbit (MEO): from 5000 to 15000 km, they include navigation satellites (GPS, Galileo, Glonass). • Low Earth Orbit (LEO): from 500 to 1000 km above Earth, includes military intelligence satellites, weather satellites.

30. Satellite Orbits

31. GEO - Geostationary Orbit • In the equatorial plane • Orbital Period = 23 h 56 m 4.091 s = 1 sidereal day* • Satellite appears to be stationary over any point on equator: • Earth Rotates at same speed as Satellite • Radius of Orbit r = Orbital Height + Radius of Earth • Avg. Radius of Earth = 6378.14 Km • 3 Satellites can cover the earth (120° apart)

32. NGSO - Non Geostationary Orbits • Orbit should avoid Van Allen radiation belts: • Region of charged particles that can cause damage to satellite • Occur at • ~2000-4000 km and • ~13000-25000 km

33. LEO - Low Earth Orbits • Circular or inclined orbit with < 1400 km altitude • Satellite travels across sky from horizon to horizon in 5 - 15 minutes => needs handoff • Earth stations must track satellite or have Omni directional antennas • Large constellation of satellites is needed for continuous communication (66 satellitesneeded to cover earth) • Requires complex architecture • Requires tracking at ground

34. HEO - Highly Elliptical Orbits • HEOs (i = 63.4°) are suitable to provide coverage at high latitudes (including North Pole in the northern hemisphere) • Depending on selected orbit (e.g. Molniya, Tundra, etc.) two or three satellites are sufficient for continuous time coverage of the service area. • All traffic must be periodically transferred from the “setting” satellite to the “rising” satellite (Satellite Handover)

35. Satellite Orbits Source: Union of Concerned Scientists [www.ucsusa.org]

36. Why Satellites remain in Orbits?

37. Advantages of Satellite Communication • Can reach over large geographical area • Flexible (if transparent transponders) • Easy to install new circuits • Circuit costs independent of distance • Broadcast possibilities • Temporary applications (restoration) • Niche applications • Mobile applications (especially "fill-in") • Terrestrial network "by-pass" • Provision of service to remote or underdeveloped areas • User has control over own network • 1-for-N multipoint standby possibilities

38. Disadvantages of Satellite Communication • Large up front capital costs (space segment and launch) • Terrestrial break even distance expanding (now approx. size of Europe) • Interference and propagation delay • Congestion of frequencies and orbits

39. When to use Satellites • When the unique features of satellite communications make it attractive • When the costs are lower than terrestrial routing • When it is the only solution • Examples: • Communications to ships and aircraft (especially safety communications) • TV services - contribution links, direct to cable head, direct to home • Data services - private networks • Overload traffic • Delaying terrestrial investments • 1 for N diversity • Special events

40. When to use Terrestrial • PSTN - satellite is becoming increasingly uneconomic for most trunk telephony routes • but, there are still good reasons to use satellites for telephony such as: thin routes, diversity, very long distance traffic and remote locations. • Land mobile/personal communications - in urban areas of developed countries new terrestrial infrastructure is likely to dominate (e.g. GSM, etc.) • but, satellite can provide fill-in as terrestrial networks are implemented, also provide similar services in rural areas and underdeveloped countries

41. Frequency Bands Allocated to the FSS • Frequency bands are allocated to different services at World Radio-communication Conferences (WRCs). • Allocations are set out in Article S5 of the ITU Radio Regulations. • It is important to note that (with a few exceptions) bands are generally allocated to more than one radio services. • CONSTRAINTS • Bands have traditionally been divided into “commercial" and "government/military" bands, although this is not reflected in the Radio Regulations and is becoming less clear-cut as "commercial" operators move to utilize "government" bands.

42. Satellite History Calendar • 1957 • October 4, 1957: - First satellite - the Russian Sputnik 01 • First living creature in space: Sputnik 02 • 1958 • First American satellite: Explorer 01 • First telecommunication satellite: This satellite broadcast a taped message: Score • 1959 • First meteorology satellite: Explorer 07 • 1960 • First successful passive satellite: Echo 1 • First successful active satellite: Courier 1B • First NASA satellite: Explorer 08 • April 12, 1961: - First man in space • 1962 • First telephone communication & TV broadcast via satellite: Echo 1 • First telecommunication satellite, first real-time active, AT&T: Telstar 1 • First Canadian satellite: Alouette 1 • On 7th June 1962 at 7:53p the two-stage rocket; Rehbar-I was successfully launched from Sonmiani Rocket Range. It carried a payload of 80 pounds of sodium and soared to about 130 km into the atmosphere. With the launching of Rehbar-I, Pakistan had the honour of becoming the third country in Asia and the tenth in the world to conduct such a launching after USA, USSR, UK, France, Sweden, Italy, Canada, Japan and Israel. • Rehbar-II followed a successful launch on 9th June 1962 • 1963 • Real-time active: Telstar 2 • 1964 • Creation of Intelsat • First geostationary satellite, second satellite in stationary orbit: Syncom 3 • First Italian satellite: San Marco 1

43. Satellite History Calendar • 1965 • Intelsat 1 becomes first commercial comsat: Early Bird • First real-time active for USSR: Molniya 1A • 1967 • First geostationary meteorology payload: ATS 3 • 1968 • First European satellite: ESRO 2B • July 21, 1969: - First man on the moon • 1970 • First Japanese satellite: Ohsumi • First Chinese satellite: Dong Fang Hong 01 • 1971 • First UK launched satellite: Prospero • ITU-WARC for Space Telecommunications • INTELSAT IV Launched • INTERSPUTNIK - Soviet Union equivalent of INTELSAT formed • 1974 • First direct broadcasting satellite: ATS 6 • 1976  • MARISAT - First civil maritime communications satellite service started • 1977  • EUTELSAT - European regional satellite • ITU-WARC for Space Telecommunications in the Satellite Service • 1979 • Creation of Inmarsat (International Marine Satellite)

44. Satellite History Calendar • 1980  • INTELSAT V launched - 3 axis stabilized satellite built by Ford Aerospace • 1983  • ECS (EUTELSAT 1) launched - built by European consortium supervised by ESA • 1984  • UK's UNISAT TV DBS satellite project abandoned • First satellite repaired in orbit by the shuttle: SMM • 1985 • First Brazilian satellite: Brazilsat A1 • First Mexican satellite: Morelos 1 • 1988 • First Luxemburg satellite: Astra 1A • 1989  • INTELSAT VI - one of the last big "spinners" built by Hughes • Creation of Panamsat - Begins Service • 1990 • IRIDIUM, TRITIUM, ODYSSEY and GLOBALSTAR S-PCN projects proposed - CDMA designs more popular • EUTELSAT II • On 16 July 1990, Pakistan launched its first experimental satellite, BADR-I from China • 1992  • OLYMPUS finally launched - large European development satellite with Ka-band, DBTV and Ku-band SS/TDMA payloads - fails within 3 years • 1993  • INMARSAT II - 39 dBW EIRP global beam mobile satellite - built by Hughes/British Aerospace • 1994  • INTELSAT VIII launched - first INTELSAT satellite built to a contractor's design • Hughes describe SPACEWAY design • DirecTV begins Direct Broadcast to Home • 1995 • Panamsat - First private company to provide global satellite services.

45. Satellite History Calendar • 1996  • INMARSAT III launched - first of the multibeam mobile satellites (built by GE/Marconi) • Echostar begins Diresct Broadcast Service • 1997  • IRIDIUM launches first test satellites • ITU-WRC'97 • 1999  • AceS launch first of the L-band MSS Super-GSOs - built by Lockheed Martin • Iridium Bankruptcy - the first major failure? • 2000  • Globalstar begins service • Thuraya launch L-band MSS Super-GSO • 2001 • XM Satellite Radio begins service • Pakistan’s 2nd Satellite, BADR-B was launched on 10 Dec 2001 at 9:15a from Baikonour Cosmodrome, Kazakistan • 2002 • Sirius Satellite Radio begins service • Paksat-1, was deployed at 38 degrees E orbital slot in December 2002 • 2004  • Teledesic network planned to start operation • 2005  • Intelsat and Panamsat Merge • VUSat OSCAR-52 (HAMSAT) Launched • 2006 • CubeSat-OSCAR 56 (Cute-1.7) Launched • K7RR-Sat launched by California Politechnic University • 2007 • Prism was launched by University of Tokyo • 2008 • COMPASS-1; a project of Aachen University was launched from Satish Dawan Space Center, India. It failed to achieve orbit.

47. Q&A • ????