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Inter Satell!Te L!Nk
 

Inter Satell!Te L!Nk

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This presentation covers all the necessary topics related to satellite links from the basics to the research oriented topics like simulation etc.

This presentation covers all the necessary topics related to satellite links from the basics to the research oriented topics like simulation etc.

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    Inter Satell!Te L!Nk Inter Satell!Te L!Nk Presentation Transcript

    • Note: I(Part 2) along with Mr. Sanjeev Gupta (Part 1) delivered this presentation , during our MS (ME/Mtech) in Communication Engineering at Birla Institute of Technology and Science Pilani India !NTER SATELL!TE L!NK SEASON 1 “It’s all about global coverage” Sanjeev Kumar 2006H124469 Dated : November 2007 Place: Birla Institute of Technology and Science Pilani India
    • Agenda for Season 1 • What is Inter Satellite Link (ISL) ? • The Need of ISLs and IOLs ! • Satellite Cancellations and examples ! • Constellation and Table • Constellation Characteristics • Band of Working ! • Applications of ISL and IOL ! • Pros and Cons of ISL • Types of ISL ! • Optical Inter Satellite Link ! • MIT Lincoln Laboratory‟s 1 Gbps DPSK test-bed ! • Case Study Of Iridium
    • What is Inter Satellite Link (ISL) ? • A service providing links between artificial satellites. • Inter-satellite links (ISL) within the constellation, or inter-constellation links with other data relay satellites to carry traffic and signaling. • Also known as cross link. • Abbreviated as ISL • ISL operates in the Ka-band at frequencies in the range 23.18– 23.38 GHz.
    • The Need of ISLs and IOLs ! • Satellites can be used to connect with each other, through the use of ISL or inter-orbit links (IOL), which when combined with on-board routing facilities, can be used to form a network in the sky. (Known as Satellite Personal Communication Network – S PCN) • The more sophisticated the space segment, the less reliant it is on the ground network, thus reducing the need for gateways. • More will be in Application Episode.
    • Satellite Cancellations and examples ! • A constellation is a group of similar satellites working together in partnership to provide a network of useful service. • Each satellite in a constellation, for example, acts as a switching node and is connected to nearby satellites by inter satellite links. An example is the two LEOs cross- linked in Fig. S1.1 • Examples • U.S Defense satellite operational network called FLTSATCOM (Fleet satellite communications system) • SBIRS (Space-based infrared system) • Iridium • Teledesic networks
    • Satellite Cancellations and examples ! Fig S1.1a A sketch of SBIRS, an example of inter satellite links and satellite constellation.
    • Satellite Cancellations and examples ! Fig S1.1b. satellites in Iridium Cancellation
    • Constellation and Table !
    • Constellation Characteristics !
    • Band of Working “ISL operates in the Ka-band at frequencies in the range 23.18–23.38 GHz.”
    • Applications of ISL and IOL ! Figure S1.2 Possible S-PCN architectures for global coverage. •To connect GEO and possibly non-GEO satellites to each other. •The commercial application of ISLs is for the Iridium system, and these employ Ka-band.
    • Positives and Negatives with ISL Positives /Advantages • Adds further dimensions to the definition of location areas and mobility management in satellite networks • Calls may be grounded at the optimal ground station through another satellite for call termination – reducing the length of the terrestrial „tail‟ required. • A reduction in ground-based control may be achieved with on-board baseband switching – reducing delay (autonomous operation). • Increased global coverage – oceans and areas without Earth stations. • Single network control centre and Earth station.
    • Positives and Negatives with ISL Negatives/Problems • The complexity and cost of the satellites will be increased. • Power available for the satellite/user link may be reduced. • Handover between satellites due to inter-satellite dynamics will have to be incorporated. • Replenishment strategy. • Frequency co-ordination. • Cross-link dimensioning. “Despite these disadvantages, the advantage of routing traffic in the sky independently of the ground infrastructure, makes the use of ISLs an attractive solution.”
    • Types of ISL ! There are two types of ISL •RF ISL •Optical ISL • RF is generally not used now a days , the whole research community is working on Optical ISL because of the advantages it provide
    • Optical Inter Satellite Link ! • Space-based optical communications • High data rate (many Gbps) space-earth links • Much narrower beam-width than the RF system • Potential for interference to or from adjacent satellites will be reduced • Requirements for more accurate pointing • Pointing, acquisition and tracking (PAT) and the impact that this may have on the spacecraft could impose an unwelcome burden • The optical spectrum is currently unregulated
    • Japan‟s Communications Research Laboratory (CRL) Fig. S1.4. Japanese Optical Communications System Plan (CRL).
    • Japan‟s Communications Research Laboratory (CRL) • Fairly broad-ranging program • Current plans call for investigation of multichannel medium bit rate (300 Mbps) systems using 0.8 μm wavelength technology • Simultaneously developing high rate (1.2 Gbps) systems using 1.5 μm technology • The plan is for operational 10 Gbps/channel systems.
    • Japan‟s Communications Research Laboratory (CRL) Fig. S1.5. Performance targets.
    • MIT Lincoln Laboratory‟s 1 Gbps DPSK test- bed Fig. S1.6. Lincoln Laboratory 1 Gbps test-bed system.
    • MIT Lincoln Laboratory‟s 1 Gbps DPSK testbed • Programs for U.S. military optical communications needs • Based upon a 1.55 μm wavelength • Erbium-doped fiber amplifier technology
    • Case Study Iridium
    • Case Study Iridium •What is Iridium ? •How it works ? •Network Performance! •Whats Next ?
    • Case Study Iridium •Deployed in 1998 •Consists of 66 satellites in six orbital planes •Each satellite has 48 spot beams •The inter-satellite links operate in the 23.18- to 23.38-GHz band •The uplink and downlink frequency bands to the gateways are 29.1 to 29.3 GHz and 19.2 to 19.6 GHz, respectively
    • Case Study Iridium •A satellite-based, wireless personal communications network • Providing a robust suite of voice and data features all over the globe •Comprised of three principal components -- the satellite network --the ground network --Iridium subscriber products, including phones and data modems.
    • Case Study Iridium •More than 99 percent of calls placed through Iridium handsets were successfully connected compared to 51.3 percent of all calls from a competitor's handset. •98.1 percent of calls on Iridium handsets were successfully connected and completed without being dropped during a three- minute period compared to 36.2 percent of calls on a competitor's handset. REASONS OF ITS ADVANTAGES •More satellites than any other commercial constellation • Constantly in view of every part of the Earth. •With no service gaps, Iridium users should be able to pick up and hold a strong communications signal
    • Case Study Iridium •Iridium is often used as a backup to cellular data modems – many businesses that need a very reliable connection automatically switch over to Iridium when their GSM data service fades or is unavailable. •With terrestrial mobile systems only covering about 15 percent of the Earth's surface (and certainly not the sky, oceans or poles), Iridium is the only connection available to many parts of the world. Even in urban and suburban environments, Iridium data solutions are providing reliable backup.
    • Case Study Iridium Future Network •Plans for 288 satellites to be deployed in a number of polar orbits •Each satellite is interconnected to eight adjacent satellites to provide tolerance to faults and adaptability to congestion. •The earth is divided into approximately 20,000 square „„supercells‟‟, each 160 km long and comprised of 9 square cells. • Each satellite‟s beam covers up to 64 supercells
    • !NTER SATELL!TE L!NK SEASON 2 “It’s all about global coverage” Ashwini Patankar 2006H124470
    • Agenda of Season 2 • ISL Design • ISL Trade Offs • Issues in ISL • Simulation and Simulation Strategies • Architecture • Topology • Defining Constellation • Routing and Routing Algorithms • Routing Approach for Simulation • Simulation Parameters • Evaluation Tools • Research Related Tools in ISL • Conlcusion
    • ISL Design Constrained in ISL design • Low transmitting power Pt • Low figure of merit (G / T) values. • Satellite EIRP. • Size of antenna on satellite. • Other Trade offs to be discussed in subsequent sections.
    • ISL Design D, Antenna Diameter Φc, Beam width pointing to each other h, altitude of the orbit Dc, propagation distance γs,,angle Te, equivalent noise temperature Pt, Transmitted power ( A to B) Assumptions: Same orbit, no aerodynamic drag, identical antenna, exact position of each other Fig. S2. A model of an inter satellite link
    • ISL Design • Then by geometry • Eq 1 • At maximum line of sight the propagation distance is • Eq 2 • At higher altitudes h >> Re => 2h Eq 3 • Φc ,dependent on antenna diameter and propagation frequency, i.e. • Eq 4 • We know that receiving antenna gain is related to the aperture area.
    • ISL Design • There fore transmitting and receiving antenna gains are resp. • Eq 5 • Eq 6 • Also, • Eq 7 • From the above equations carrier-to-noise ratio C=N delivered to the receiving satellite over the ISL as
    • ISL Design • In practice, satellite cross-links are typically in the K-band in the GHz frequency range, we can conveniently express the propagation wavelength λ as (0.3 / f), where f is in GHz. Hence, • From this expression, the most practical means of delivering high C/N to the receiving satellite over ISL is by one of the following because in practice we are constrained by the size of the antenna that can be deployed……………
    • ISL Design • Decreasing the separation distance dc • Increasing the transmission frequency f • Lowering the system front-end noise temperature Te since N is directly proportional to Te .
    • ISL Trade Offs • Separation distances and angles for different satellites. (Eq 1)
    • ISL Trade Offs • Graph produce for better view
    • ISL Trade Offs • Date rate • D, antenna diameter
    • ISL Trade Offs
    • Issues in ISL ! • Telecommunication industry faced a challenge to provide a variety of new, broadband multimedia services for users equipped with fixed and mobile terminals. • Requirements for higher capacity and lower propagation delay made non-geostationary satellite constellations appealing, especially with advances in technology which enabled the implementation of ISLs. • Many satellite communication systems have been proposed in the last few years, both for the provision of mobile telephony and internet-in-the sky. • Several of these proposals already incorporate ISLs suitable for traffic interconnection in the satellite segment of the network. (like iridium)
    • Issues in ISL ! • However, non-geostationary satellite systems with ISLs still lack • efficient routing algorithms, • adaptive to inherent dynamics of topology and traffic load. • Current solutions are mainly reusing algorithms developed and optimized for the use in terrestrial networks with static topology, thus having only limited capability to grasp the characteristics of non-geostationary satellite system. • In addition, dynamic topology of satellite networks and variations in traffic load in satellite coverage areas due to the motion of satellite in their orbits, pose stringent requirements to routing algorithms
    • Simulation and Simulation Strategies ! • Various simulations have been carried out to study the performance of different routing algorithms in MEO and LEO satellite networks. • In general, the simulation models consist of the following components: • The satellite system dynamics components which describe the satellite constellation characteristics; • The traffic simulation component which considers the geographical distribution of traffic sources and the daily variation of their traffic intensity as well as the traffic source generation; • The ISL network component which studies the performance of simulated routing algorithm under various network conditions.
    • Architecture
    • Topology Constellation Topology Up/ Down Links Topology Ground Topology Fig S2. The Topology Module Next Step Define a Constellation ……..
    • Defining Constellation ! • The Parameters needed to define Constellations are: • Number of orbital planes; • Declination of orbital planes; • Ascension angle at the seam; • Orbit altitude; • Number of satellites per orbit; • Phase between the corresponding satellites of each orbit.
    • Routing and Routing Algorithms ! • Static and Adaptive Routes • Isolated and Non isolated Routes • Pre Computed and On Demand Routes • Centralized, Decentralized and Distributed Routing Laurent Franck, Gerard Maral, quot;Routing in Networks of Intersatellite Linksquot;, IEEE Transactions On Aerospace And Electronic Systems Vol. 38, No. 3 July 2002
    • Routing Approach For Simulation ! Fig S2. ISL Routing Approach
    • Simulation Parameters !
    • Evaluation Tools ! • NETWORK SIMULATOR 2 • MATLAB • UNIX/C • OPNET • BoNeS (BoNeS SATLAB) • LeoSim (simulator for routing) • GaliLEO • CONSIMTM (tool for reliability) • AristoteLEO • SEESAWS
    • Research Related Issues in ISL ! • Routing Algorithm • Congestion Control Algorithms • Resource Allocation and Utilization • QoS related Issues • Constellation topologies • ISL‟s protocol models • TCP / IP and ISL • Satellite IP
    • Conclusion ! • ISL and IOL adds one more option to the wireless communication networks. • They not only provide higher data rates but also provide global coverage. • TCP/IP like networking protocols are giving boost to satellite internet access. • The different issues discussed earlier, are the major challenges related to ISL. • Efficient network utilization is needed in ISL like routing algorithms, congestion control mechanisms.
    • References ! • Michael O. Kolawole, quot;Satellite Communication Engineeringquot;, Marcel Dekker, Inc.,2002 • Ray E. Sheriff and Y. Fun Hu, quot;Mobile Satellite Communication Networksquot;, John Wiley & Sons, 2001 • Y. Fun Hu, Gerard Maral and Erina Ferm, quot;Service Efficient Network Interconnection via Satellitequot;,John Wiley & Sons, 2002 • Bruce R. Elbert, quot;The Satellite Communication Handbookquot;, Artech House, Inc.,2004
    • References ! • www.iridium.com • www.nasa.gov.in • http://www.wtec.org/loyola/satcom2/03_06.htm • http://telecom.esa.int/telecom/www/object/index .cfm?fobjectid=431
    • References ! • P.V.Gatenby, quot;Optical Inter satellite Links For Military Satellite Communications” • R. Ferrier, A. D. Johnson, G. D. Fletcher, Marconi Spaci, quot;Inter satellite Coherent Optical Communication” • Erich Lutz, “Issues in satellite personal communication systems”, Wireless Networks 4 (1998) 109–124 109 • Jaeook Lee, Sun Kang,“Satellite over Satellite (SOS) Network: A Novel Architecture for Satellite Network”, IEEE Infocom 2000 • Laurent Franck, Gerard Maral, quot;Routing in Networks of Intersatellite Linksquot;, IEEE Transactions On Aerospace And Electronic Systems Vol. 38, No. 3 July 2002
    • !NTER SATELL!TE L!NK Season 3 (Back Up) “It’s all about global coverage” Sanjeev Kumar & Ashwini Patankar 2006H124469 & 2006H124470
    • Satellite Cancellations and examples ! • FLTSATCOM • U.S. Navy and Air Force units (except for the polar regions) • Four satellites. • Injected into a near-geosynchronous equatorial orbit • positioned at longitudes 100oW, 23oW, 71:5oE, and 172oE. • Each satellite overlaps in coverage with the adjacent satellite. • The coverage is between the latitudes of 70oN and 70oS. • Primary Navy‟s broadcast and ship interchange communications system. • Vital communications to the Allied Forces worldwide.
    • Satellite Cancellations and examples ! • SBIRS • U.S. missile defense • system: a sort of missile shield [3]. SBIRS would comprise a network of • satellites: LEO, HEO, and GEO (see Fig. 2.7). In theory, the GEO forms the • frontline satellites that provide the first warning of missile launches over the • equator and HEO satellites cover the North Pole.The information received the frontline satellites is then passed via dedicated defense support program • (DSP) satellites to earth terminals. The DSP satellites are programmed to look • for the launch flares of a missile taking off or the distinctive double flares that • mark the explosion of a nuclear weapon. The details of the
    • The Need of ISLs and IOLs !
    • ISL Design and Trade Offs ! • Pointing Error
    • Routing And Use of ATM • The inclusion of a satellite on-board switch with some ATM functionality was considered for the satellite architecture within COST253. These switches would route packets (or ATM cells) using the information in the header. Options on-board the satellite for routing, include routing via individual spotbeams to ground stations, or via ISLs to other satellites which will further route the packets.
    • Routing And Use of ATM
    • Economy of (your country) • Explain which goods and services are produced in your country. How do people typically provide for the needs of themselves and their families?