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Iridium satellite system (iss)


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Iridium satellite system (iss)

  1. 1. WIRELESS COMMUNICATIONTOPIC: IRIDIUM SATELLITE SYSTEM (ISS)-THE ULTIMATE WIRELESS NETWORKPresented By:S.M.VAMSEE RAMA KRISHNA T.RANJITH, ECE, E.C.EAURORA’S ENGINEERING COLLEGEBHONGIR, NALGONDA DISTRICT, ANDHRA PRADESH.E-mail: E-mail: t_ranjithkumar@yahoo.comCell no: 9948156678 Cell no: 9849782889Address for contact:H.NO.1-1-336/127,vivek nagar,Chikkadpally,Hyderabad,500020
  2. 2. THE IRIDIUM SATELLITE SYSTEM (ISS)ABSTRACT: -The credential part of the paper lies in theapplications part where the application(forthcoming) of ISS as an alert system forEARTHQUAKE and TSUNAMI likenatural disasters with which the casualties canbe reduced drastically.Every year thousands of people diebecause an earthquake catches them in adangerous place or during a defence-lesssleep. Here’s an alert system that could warnbefore an earthquake strikes, or TSUNAMIblows.Iridium is a satellite based wireless personalcommunications network designed to permit awide range of mobile telephone servicesincluding voice, data, networking, facsimile,geo location, fax capabilities and paging. TheIridium project, which even sounds likesomething out of star wars, has its mainobjective to allow handheld mobiles to beused from anywhere on the planet, with thecall being routed directly from handset tohandset via one or several of the satellites.The iridium mobile telephone system isundoubtedly the Cadillac of mobile telephonesystems. With complete coverage of theEarth’s oceans, airways and Polar Regions,Iridium delivers essential services to userswho need communications access to and fromremote areas where no other form ofcommunication is available. With this systemcaller can call to any person, anywhere at anytime in the world.This paper unleashes the system facts suchas the network coverage, satelliteconstellation of ISS system and its operationalong with its advantages and applications.Last but not least the innovative applicationof ISS as TSUNAMI, EARTHQUAKE alertsystem is explained in brief.INTRODUCTION: -The fundamental purpose of anelectronic communications system is totransfer information from one place toanother. Thus, electronic communicationscan be summarized as the transmission,reception, and processing of informationbetween two or more locations usingelectronic circuits.TYPICAL COMMUNICATION MODEL:-
  3. 3. electronic devices or circuits that convertsoriginal source information to a signal that ismore suitable for transmission over a giventransmission medium. The transmissionmedium provides a means of transferringsignals from a transmitter to a receiver. Areceiver is a collection of one or moreelectronic devices or circuits that accept thetransmitted signals from the transmission,medium and converts them back to theoriginal form.SATELLITE COMMUNICATION: -A Satellite communication system consistsof one or more satellite space vehicles(transponder), a ground based station tocontrol the operation, and a user network ofearth stations that provides the interfacefacilities for transmission and reception ofterrestrial communications traffic through thesatellite system. In essence, a communicationsatellite is a microwave repeater in the skythat consists of a diverse combination ofamplifier, receiver, transmitter, regenerator,filter, multiplexer, demultiplexer and so on.A satellite communication systemwith single-channel satellite transponder cancommunicate with one transmitter andreceiver i.e. each earth station cancommunicate with only one other earthstation. To overcome this disadvantagemultiple-channel satellite transponders areintroduced. For multi-channel system,multiple carriers are used and to handlemultiple channels and so multiple-accessingformat should be established.SATELLITE COMMUNICATION SYSTEMPERSONAL COMMUNICATIONSATELLITE SYSTEM : -Mobile satellite systems (MSS)provide the vehicle for a new generation ofwireless telephone services called personalcommunications satellite systems (PCSS).The Personal Communication Satellite
  4. 4. System (PCSS) is the mother of the Iridiumsatellite system.MSS satellites are, in essence, radiorepeaters in the sky and their usefulness formobile communications depends on severalfactors such as the space vehicle altitude,orbital pattern, transmit power, receiversensitivity, modulation technique, antennaradiation pattern, and several other factors.Satellite communication systems havetraditionally provided narrowband andwideband voice, data, video, facsimile, andnet communicating via high altitude,geosynchronous earth_orbit (GEO), andsatellites. Personal communications satelliteservices, however, use low earth_orbit (LEO)and medium earth_orbit (MEO) satellites thatcommunicate directly with small, low powermobile telephone units. PCSS telephones willbe able to make or receive calls at anytime,anywhere in the world.HISTORY BEHIND ITS NAME:The system is callediridium after the element on the periodic tablewith the atomic number 77, because iridium’soriginal design called for 77 satellites. Thefinal design, however, requires only 66satellites.OPERATION: -The 66-vehicle LEO inter-linkedsatellite constellation can track the location ofa subscriber’s telephone handset, determinethe best routing through a network of ground-based gateways and inter-satellite links,establish the best path for the telephone call,Initiate all the necessary connections, andterminate the call upon completion. Theunique feature of iridium satellite system is itscross-links. With this two-way globalcommunications is possible even when thedestination subscriber’s location is unknownto the caller.The Iridium System is a satellite-based,wireless personal communications network topermit a wide range of mobile telephoneservices including voice, data, networking,facsimile, and paging, Virtually anydestination anywhere on earth. allowingtelecommunication anywhere, any time, andany place Each satellite is cross-linked to fourother satellites; two satellites in the sameorbital plane and two in an adjacent plane Torelay digital information around the globe.The cross-link antennas point toward theclosest spacecraft orbiting in the same planeand the two adjacent co-rotating planes.Feeder link antennas relay information to theterrestrial gateways and the system controlsegment located at earth station.
  5. 5. .IRIDIUM SATELLITECONSTELLATION: -The Iridium system comprises three principalcomponents: the satellite network, the groundnetwork and the Iridium subscriber productsincluding phones and pagers. Voice and datacalls are relayed from one satellite to anotheruntil they reach the satellite above the IridiumSubscriber Unit (handset) and the signal isrelayed back to Earth.The Iridium constellation consistsof 66 operational satellites and 14 sparesorbiting in a constellation of six polar planes.Each plane has 11 mission satellitesperforming as nodes in the telephonynetwork. The 14 additional satellites orbit asspares ready to replace any unserviceablesatellite..Iridium USES 66 operational satellitesconfigured at a mean elevation of 420 milesabove earth in six nearly polar orbital times of100 min 28 sec. This allows iridium to coverthe entire surface area of earth and wheneverone satellite goes out of view of a subscriber adifferent one replaces it. The satellites areplaced appropriately in north south directionsforming co-rotating planes up one side ofearth, across the poles, and down the otherside. The first and last planes rotate inopposite directions, creating a virtual beam.The co-rotating planes are separated by 31.6degrees and the beam planes are 22 degreesapart.GLOBAL COVEARGE OF ISS: -Each satellite is equipped with 3 L-bandantennas forming a honeycomb pattern thatconsists of 48 individual spot beams with atotal of 1628 cells aimed directly below thesatellite. As the satellite moves in its orbit, thefootprints move across earth’s surface andsubscriber signals are switched from onebeam to the next or from one satellite to the
  6. 6. next in a handoff process. When satellitesapproach the north or South Pole, theirfootprints converge and the beams overlap.Outer beams are then turned off to eliminatethis overlap and conserve power on thespacecraft. Each cell has 174 full duplexvoice channels for a total of 283,272 channelsworldwide. The satellites are in a near-polarorbit at an altitude of 485 miles (780 km).They circle the earth once every 100 minutestraveling at a rate of 16,832 mph. Thisconstellation ensures that every region on theglobe is covered by at least one satellite at alltimesIRIDIUM SYSTEM ARCHITECTURE: -The iridium usesGSM-based telephony architecture to providea digitally switched telephone network andglobal roaming feature is designed in to thesystem. Each subscriber is assigned apersonal phone number and will receive onlyone bill, no matter in what country or areathey use the telephone.SYSTEM LAYOUT: -The ground network is comprised ofthe System Control Segment and telephonygateways used to connect into the terrestrialtelephone systemIt provides global operational support andcontrol services for the satellite constellation,delivers satellite-tracking data to thegateways, and performs the terminationcontrol function of messaging services. TheSystem Control Segment consists of threemain components: 4Telemetry Tracking andControl sites, the Operational SupportNetwork, and the Satellite Network OperationCenter. The primary linkage between theSystem Control Segment, the satellites, andthe gateways is via K-Band feeder links andcross-links throughout the satelliteconstellation. Subscriber telephone setsused in the iridium system transmit andreceive L-band frequencies and utilize bothfrequency and time division multiplexing tomake the most efficient use of a limitedfrequency spectrum. Other communicationslinks used in iridium include EHF and SHFbands between satellites for telemetry,command, and control, as well as routingdigital voice packets to and from gateways.Iridium gateways are primeexamples of advances in satelliteinfrastructures that are responsible for the
  7. 7. delivery of a host of new satellite services.The purpose of the gateways is to support andmaintain roaming subscribers as well as tointerconnect iridium subscribers to the publicswitched telephone network. Gatewayfunctions include the following:1. Set up and maintain basic andsupplementary telephony services.2. Provide an interface for two-waytelephone communications between twoiridiumSubscribers and iridium subscribers tosubscribers of the public switched telephoneNetwork.3. Provide iridium subscribers withmessaging, facsimile, and data services.4. Facilitate the business activities of theiridium system through a set of cooperativemutual agreements.IRIDIUM SATELLITE NETWORKCOVERAGE:IRIDIUM SYSTEM SPOT BEAMFOOTPRINT PATTERNEach satellite is equipped with 3 L-bandantennas forming a honeycomb pattern thatconsists of 48 individual spot beams, with atotal of 1628 cells aimed directly below thesatellite as shown in above figure each of thespot beam approximately measuring around30miles or 50k.m. As the satellite moves inits orbit, the footprints move across earth’ssurface and subscriber signals are switchedfrom one beam to the next or from onesatellite to the next in a handoff process.When satellites approach the North or SouthPole, their footprints converge and the beamsoverlap. Outer beams are then turned off toeliminate this overlap and conserve power onthe spacecraft. Each cell has 174 full-duplexvoice channels for a total of 283,272 channelsworldwide.FREQUENCY PLAN ANDMODULATION: -All ka-band up-links and cross-linksare packetized TDM/FDMA using quadraturephase shift keying and FEC1/2 rateconvolutional coding with viterbi decoding.Coded data rates are 6.25 Mbps for gatewaysand satellite control facility links and 25Mbps for satellite cross-links. Both up-linkand downlink transmissions occupy100MHZof bandwidth and inter-satellite linksuse 200MHZ of bandwidth. The frequencybands are as follows:
  8. 8. L-band subscriber to satellite voicelinks=1.616GHZ TO 1.6265GHZKa-band gateway downlinks=19.4 GHZ to19.6GHZ.Ka-band gateway up-links=29.1GHZ to29.3GHZKa-band inter-satellite cross-links=23.18GHZ to 23.38GHZComparison between iridium andtraditional satellite systems: - Using satellite cross links is the uniquekey to the iridium system and the primarydifferentiation between iridium and thetraditional satellite bent pipe systemwhere all transmissions follow a pathfrom earth to satellite to earth. Iridium is the first mobile satellite toincorporate sophisticated, onboard digitalprocessing on each satellite. Entire global coverage by a singlewireless network system. Only provider of truly global voice anddata solutions. With this system the subscriber will neverlisten a message called ”OUT OFCOVERAGE AREA”This list provides just a few ofabsolutely inexhaustible list of comparisons.ADVANTAGES: - Less reliance on wire-line networks Continuous talk time Fewer outages Don’t need to be in the in the samefootprint as the gatewayDISADVANTAGES: - High risk associated with designing,building, and launching satellites. High cost for the terrestrial-basednetworking and interface infrastructure. low power, dual mode transceivers aremore cumbersome and expensive
  9. 9. APPLICATIONS: - Fixed cellular telephone service Complementary and back uptelephone service in fields of: Retail Manufacturing Military Government Transportation Insurance FinanceFORTH COMING APPLICATION:EARTHQUAKE and TSUNAMI ALERTTHROUGH ISS:Earthquakes and Tsunamis strike withoutwarning. The resulting damage can beminimized and lives can be saved if thepeople living in the earth quake-prone areaare already prepared to survive the strike.This requires a warning before the strongground motion from the earthquake arrives.Such a warning system is possible becausethe energy wave released at the epicentertravels slower (at 3.5 to 8km/s) than light.The warning signal from the earthquakeor tsunami epicenter can be transmitted todifferent places using the satellitecommunication network, fiber-opticsnetwork, pager service, cell phone service ora combination of these. The satellite basedwireless network such as ISS is idle if systemhas to cover a large continent like ASIA.For EARTHQUAKE,TSUNAMI-prone countries like Indonesia,Japan seismic alert system using the ISSnetwork spread throughout the earth isproposed here. This system does not try tofind the epicenter or the fault line caused bythe earthquake.PRINCIPLE:Energy waves released travel slower thanlight waves .It simply monitors the earthvibrations and generates alert signal when thelevel of earth vibrations crosses a threshold.COMMUNICATING THE DANGER:This GSM-based ISS alert system monitorsthe earth vibration using a strong motion
  10. 10. accelerometer at the earthquake-prone areaand broadcasts an alert message to towns andvillages through the cell phone networkexisting throughout the state. Here wirelessmobile phones (ISS phones) are used astransmitter and receivers.The communication systemfor earthquake alert comprises an earthquakeSensor and interface unit, decision system andalert-dissemination network.After receiving alert, a middle-agedperson takes 30 to 40seconds to godown thestairs from fifth floor and 65 to 80 secondsfrom tenth floor. If it takes a minimum of 10seconds to damage a poorly structured house,this 10 seconds too can be consider for goingto safer place. If we consider these points,giving earthquake alert before the actualoccurrence of earthquake can minimizecasualties. Time to alert is critical. But ingenerating the alert quickly, there arepossibilities of false alarm. In the systemproposed here, an attempt has been made toreduce the possibility of false alarm. Still, thesystem needs to be simulated and validatedbefore putting into practice.CONCLUSION: -Commercial point of view:Availability of servicesand early subscriber take-up will be the key tosurvival for operators. Lower infrastructurecosts will further help in early break-even andprofitability for network operators.Equipment vendors should therefore focus onmaking available cost effective solutions forproviding a wide range of services to attractboth business and non-business users.Evolution, not revolution is the only way toget to the market earl and with the lowestcost.Economic point of view:Since the satellites has already beenlaunched it is important that this system isapplied as much as possible. InnovativeApplications like “seismic alert ofearthquakes and tsunami” should be brought
  11. 11. out which serves the real purpose of being anengineering application. Government shouldalso play a major role to get these servicesclose towards ordinary man and should playits part in providing its citizen the bestpossible communication system in the world.References:1.Electronic Communication Systems-WAYNETOMASI—PEARSONEDUCATION2.Satellite Telecommunication. —SHELDON—TMH.20003.EFY MAGAZINE-DEC 2004 EDITION.Websites: -1. www.gmpcs-us.com2. www.iridium.comANNEXURES:Iridium Tools: