Mobile satellite communication

1. Himanshu Singh, 2011EET3679

2. Intro Appl. Types SatellitesHandoff How it Works Routing Himanshu Singh, 2011EET3679, IIT Delhi 10/11/2012 2

3.  A satellite is an object that orbits another large object like planet. A communication satellite is a station in space that is used for telecommunication, radio and television signals. In simplest form , a satellite communication can be thought of as a big microwave repeater in the sky. Himanshu Singh, 2011EET3679, IIT Delhi 10/11/2012 3

4.  They are used for mobile applications such as communication to ships, vehicles, planes, hand-held terminals and for TV and radio broadcasting. A satellite works most efficiently when the transmissions are focused with a desired area. The earth station should be in a position to control the satellite if it drifts from its orbit it is subjected to any kind of drag from the external forces. Transmission cost is independent of distance. The power and bandwidth of these satellites depend upon the preferred size of the footprint, complexity of the traffic control protocol schemes and the cost of ground stations. Himanshu Singh, 2011EET3679, IIT Delhi 10/11/2012 4

5.  Satellites orbit around the earth ◦ Orbits can be circular or elliptical. Important parameters ◦ inclination and elevation angles Inclination angle (δ): Between the equatorial plane and the plane described by the satellite orbit. Elevation angle (ε): Between the centre of the satellite beam and the plane tangential to the earth’s surface. ◦ Footprint can be defined as the area on earth where the signals of the satellite can be received. Himanshu Singh, 2011EET3679, IIT Delhi 10/11/2012 5

6.  International Telecommunication Union (ITU) Three regions ◦ Region1: Europe, Africa and Mongolia ◦ Region 2: North and South America and Greenland ◦ Region 3: Asia (excluding region 1 areas), Australia and south-west Pacific. Three common bands (in GHz): ◦ C-band: 4-8 - Fixed Satellite Service ◦ Ku-band: 12-18 - Direct Broadcast Satellite Services ◦ Ka-band: 25-40 – Military & Scientific Research Himanshu Singh, 2011EET3679, IIT Delhi 10/11/2012 6

7.  Geostationary or geosynchronous earth orbit (GEO) GEO HEO Quasi - Zenith satellite LEO MEO Low Earth Orbit (LEO) Earth Medium Earth Orbit (MEO) Highly Elliptical Orbit (HEO) Himanshu Singh, 2011EET3679, IIT Delhi 10/11/2012 7

8.  Synchronous with respect to earth Footprint is covering almost 1/3rd of the Earth ◦ 3-4 Satellites are enough to cover the earth Circular Orbit, Satellite visibility 24 hour Altitude : 36,000 km Inclination Angle : 0 Applications: ◦ TV and radio broadcast ◦ Weather forecast ◦ Backbones for the telephone networks Issues ◦ Shading of the signals ◦ High latency (270 ms) ◦ Transferring a Satellite into GEO is very expensive ◦ Cannot be used for small mobile phones (High transmit power needed ) Himanshu Singh, 2011EET3679, IIT Delhi 10/11/2012 8

9.  Circular orbit at 45 degree to equator Altitude 36000 km One satellite fixed near zenith in Japan 3-4 satellites are required Applications: ◦ mobile applications ◦ Communications-based services  Video  audio,  data Quasi-Zenith satellite orbit ◦ Positioning information. Himanshu Singh, 2011EET3679, IIT Delhi 10/11/2012 9

10.  Altitude 500-2000km Satellite visibility 10-20m, Orbital period 5-8 hour Delay : relatively low (approx 10 ms) Smaller footprints of LEOs allow for better frequency reuse, similar to the concepts used for cellular networks Applications: ◦ Remote sensing ◦ Mobile communication services (due to lower latency). LEO Issues ◦ 48 and above satellites required to cover whole earth ◦ Short life: 4-10 years Earth ◦ Larger Handoffs Examples: ◦ Iridium (start 1998, 66 satellites)  Bankruptcy in 2000, deal with US DoD for free use ◦ Globalstar (start 1999, 48 satellites)  Not many customers (2001: 44000) Himanshu Singh, 2011EET3679, IIT Delhi 10/11/2012 10

11.  Altitude 10000km-20000km Orbital period 6-12 hour MEO 10-15 satellites required Earth Satellite visibility 2-4 hrs Propagation delay less Set-up cost is medium MEO can cover larger populations, so requiring fewer handovers than LEO Issues ◦ Larger Delay: 70–80 ms ◦ Need higher transmit power ◦ Special antennas for smaller footprints Example: ◦ ICO (Intermediate Circular Orbit, Inmarsat) start ca. 2000 Himanshu Singh, 2011EET3679, IIT Delhi 10/11/2012 11

12.  Altitude 40000km Orbital period 8-24 hour 2-3 satellites required Large propagation delay Satellite lifetime 20-25 yrs HEO orbits offering visibility over Earths polar regions, which most geosynchronous satellites lack Example ◦ Molniya ◦ Tundra Himanshu Singh, 2011EET3679, IIT Delhi 10/11/2012 12

13. Himanshu Singh, 2011EET3679, IIT Delhi 10/11/2012 13

14. Satellite Segment Inter Satellite Link (ISL) Mobile User Link (MUL) MUL Ground Gateway Link (GWL) Segment GWL small cells (spotbeams) base station or gatewayfootprint ISDN PSTN GSM PSTN: Public Switched User data Telephone Network End User Himanshu Singh, 2011EET3679, IIT Delhi 10/11/2012 14

15.  Modulation: Three major classes of digital modulations ◦ Amplitude – Shift Keying ◦ Frequency – Shift Keying ◦ Phase – Shift Keying Multiple access techniques ◦ Frequency Division Multiple Access (FDMA) ◦ Time Division Multiple Access (TDMA) ◦ Code Division Multiple Access (CDMA)  WCDMA (3G ) Himanshu Singh, 2011EET3679, IIT Delhi 10/11/2012 15

17.  Benefits ◦ Less complex  Switching circuits are on the ground and the satellites are just reflectors ◦ Easier to operate  Most of the call is transferred over the public telephone network, ◦ Reduces the cost of the system.  Technical problems to be fixed on the ground Issues ◦ Gateway must be in the line of sight of the satellite ◦ Significant number of ground gateways to provide direct satellite links Himanshu Singh, 2011EET3679, IIT Delhi 10/11/2012 17

18.  Benefits ◦ Minimizes the cost of the ground segment & long distance and interconnect fees ◦ Forward connections or data packets within the satellite network as long as possible ◦ Only one uplink and one downlink per direction needed for the connection of two mobile phones Issues ◦ More complex focusing of antennas between satellites ◦ High system complexity due to moving routers ◦ Higher fuel consumption, thus shorter lifetime Himanshu Singh, 2011EET3679, IIT Delhi 10/11/2012 18

19.  Mechanisms similar to GSM Gateways maintain registers with user data ◦ HLR (Home Location Register): static user data ◦ VLR (Visitor Location Register): (last known) location of the mobile station ◦ SUMR (Satellite User Mapping Register):  Satellite assigned to a mobile station  Positions of all satellites Registration of mobile stations ◦ Localization of the mobile station via the satellite’s position ◦ Requesting user data from HLR ◦ Updating VLR and SUMR Calling a mobile station ◦ Localization using HLR/VLR similar to GSM ◦ Connection setup using the appropriate satellite Himanshu Singh, 2011EET3679, IIT Delhi 10/11/2012 19

20.  Intra satellite handover  Handover from one spot beam to another  Mobile station still in the footprint of the satellite, but in another cell Inter satellite handover  Handover from one satellite to another satellite  Mobile station leaves the footprint of one satellite Gateway handover  Handover from one gateway to another  Mobile station still in the footprint of a satellite, but gateway leaves the footprint Inter system handover  Handover from the satellite network to a terrestrial cellular network  Mobile station can reach a terrestrial network again which might be cheaper, has a lower latency etc. Himanshu Singh, 2011EET3679, IIT Delhi 10/11/2012 20

21.  Due to high mobility, handoff are extremely frequent in LEO, causing high failure rate How to Deal ?? ◦ Prioritised handover call over new call  Allocating guard channel  Queuing the handover request  Channel reservation in advance Himanshu Singh, 2011EET3679, IIT Delhi 10/11/2012 21

22. Current StatusEvaluation of 3G S-CDMA to S-WCDMA Technical evolution ofSatellite System from CDMA based evolution of Satellite system from 3G toGMR Standard 3G satellite system B3G• GMR1, GMR2 • Followed 3G and • Referring to the LTE Trends• Thuraya, AceS and developed the standardInmarsat systems of S-UMTS • Adaptive modifications for wireless transmission conditions. • MOUS of USA for military application Himanshu Singh, 2011EET3679, IIT Delhi 10/11/2012 22

23.  Weather Forecasting Radio and TV Broadcast Military App Navigation App Global Telephone Connecting Remote Areas Global Mobile CommunicationAnd Much More …… Himanshu Singh, 2011EET3679, IIT Delhi 10/11/2012 23