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8.3.1 The InternetThe Internet consists of a myriad of smaller, interconnected networks interoperatingto exchange data between host computers in the networks. TheInternet is an example of a packet-switched network. Figure 8.13 shows thebasic Internet access process. The Internet user (subscriber) accesses theInternet via his=her Internet service provider (ISP). The ISP uses routers toconnect subscribers to a dedicated-access ISDN or point of presence (POP)after concentrating subscribers’ traffic.All networks connected to the Internet share a common suite oftelecommunication protocols (standards) known as the Transmission ControlProtocol=Internet Protocol (TCP=IP). TCP=IP is a layered protocol suite likethe OSI protocol suite already discussed earlier in this chapter. The TCP=IPsuite contains a number of protocols, some of which are shown in Fig. 8.14.The network layer routes packets using IP. This layer comprises otherfunctions, for example, the Routing Information Protocol (RIP), the openshortest path first (OSPF), the Internet Control Message Protocol (ICMP), andthe Address Resolution Protocol (ARP). Both OSPF and RIP are used forgenerating routing tables. ICMP is used for reporting errors and the status ofthe stations or network. ARP is used for obtaining the medium access controlof a station from its IP address. IP uses a limited hierarchical address space,which has location information embedded in the structure.The transport layer contains TCP and ensures that a message can bereceived correctly by the destination. The application layer provides aprogramming interface for interprocess communication to the transport layerand application services for subscribers (or end users). Some of the manyapplication protocols includeFile Transfer Protocol (FTP) for file transferDomain name service (DNS) for symbolic domain name translation to acorresponding IP network addressTELNET for text-based remote access (login)Simple Mail Transfer Protocol (SMTP) for electronic mailSimple Network Management Protocol (SNMP) for network hardwareand software managementFIGURE 8.13Basic Internet arrangement.Copyright © 2002 by Marcel Dekker, Inc. All Rights Reserved.
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SatelliteCommunicationEngineeringMi
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This book is dedicated to my famili
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Because of the immense importance o
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means of a combination of applicati
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about my promise to my students, an
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2.3 Coverage Area and Satellite Net
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1Basic Principles of SatelliteCommu
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and voice (telephone) communication
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FIGURE 1.2Communication between two
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interpreting or uncovering the deci
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cryptographic keys K ti (where i ¼
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FIGURE 1.6Block ciphering technique
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FIGURE 1.7Part of block ciphering w
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Based on the ordering sequence of (
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TABLE 1.1 (continued )S612 1 10 15
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For an uncoded message x and the fe
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2. Your task is to develop a commun
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FIGURE 2.1Geometry of a satellite.
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Future trends in satellite antennas
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In the United States, the three sat
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TABLE 2.3Typical Links Frequency Ba
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FIGURE 2.4Satellite period and orbi
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FIGURE 2.6An illustration of covera
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FIGURE 2.7constellation.A sketch of
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width of 1:73 with reduced coverag
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y ¼ elevation angle of satellite f
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We can conclude that the antenna mu
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FIGURE 2.9Design flowchart of a sat
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Risk control and monitoring measure
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TABLE 2.4Antenna Selection Criteria
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Then the system availability can be
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In fact, MTBF is the reciprocal of
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2.7 ANTENNASBased on function, sate
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Two kinds of horns in common use ar
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FIGURE 2.13Geometry of a parabolic
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FIGURE 2.14 Axisymmetric reflector
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A transceiver antenna is a single a
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The gain, in the axial mode, of a h
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angles, spacecraft may shadow the s
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3. The probability of both parallel
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the baseband signal (more details a
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matrix in the communications subsys
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FIGURE 2.24Typical transfer charact
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4. Iridium LCC (1997). Iridium Syst
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3Earth StationsIn Chap. 2 we discus
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The most popular forms of modulatio
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Small earth stations are antennas w
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FIGURE 3.2BPSK space diagram.Instea
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OQPSKOffset QPSK (OQPSK) is a modif
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FIGURE 3.7An 8-PSK space diagram.an
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aud. The word ‘‘baud’’ hono
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Noise power density N 0bandwidth:N
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We observe in (3.11) that E b =N 0
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to (3.23) shows that a margin of 11
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FIGURE 3.12 Principle of scrambling
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Equalization FilterAn equalization
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that is, N zeros at the top and bot
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Example 3.2: Consider a transmissio
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which can be written as89>=R xy ðt
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ecause a voice signal is usually hi
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systems is discussed in Sec. 4.2. O
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where T e is the equivalent tempera
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operating principle of all directio
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performance of the satellite commun
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3. For two independent sources, wit
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FIGURE 3.21 A representation of mut
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In practice, Eqs. (3.78) and (3.76)
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This condition is always satisfied
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Copyright © 2002 by Marcel Dekker,
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epeaters overshooting into subseque
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6. Conventional BPSK modulation all
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4Satellite LinksA satellite link co
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FIGURE 4.2 Basic antenna parameters
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For unity efficiency, and substitut
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This expression neglects losses oth
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This expression is equally valid fo
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and Lin [5]:whereL ¼L o1 þ L oðr
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3. Calculate attenuation A r in dB
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4.2.1 Intersatellite LinksAs indica
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We know from (4.4b) that f c is dep
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FIGURE 4.9 Cross-link transmission
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Follow the uplink procedure for the
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Satellite:Frequencies:14.75 GHz up
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6. For link to be maintained betwee
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5.1 PRINCIPLES OF MULTIPLE ACCESSAs
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neously, their transmissions collid
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technique and would remain the most
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FIGURE 5.4 Typical TDMA frame struc
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FIGURE 5.6TDMA throughput for an IN
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and transmits through the satellite
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FIGURE 5.8FDMA total capacity respo
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tion; that is, log e ð1 þ xÞ x t
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REFERENCES1. Spilker, J.J. (1977).
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6.1 CHANNEL CODINGNoise within a tr
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where G is a generator matrix that
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The syndrome is a single word of le
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SolutionComparing (i) and (ii) with
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Cyclic CodesCyclic codes are a subs
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When errors occur in bursts, the nu
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FIGURE 6.3Rate 1/2 convolutional en
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us to a particular node in the tree
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FIGURE 6.6 Trellis diagram of Fig.
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FIGURE 6.9 Trellis diagram of Fig.
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A generalized Viterbi algorithm is
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3. Huffman, D.A. (1952). A method f
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4. Draw a block diagram for a convo
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1. The first essential requirement
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use. The ITU Radio Regulations gove
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Within the CCITT structure exist a
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7.2 NATIONAL AND REGIONAL REGULATIO
Page 442: 8Mobile Satellite System Services8.
Page 446: Copyright © 2002 by Marcel Dekker,
Page 450: may reside within a single LDSN. Th
Page 454: destination through the intermediat
Page 458: can be used at separate user-to-net
Page 462: where0 n 40 m 246n þ m 24ð8:
Page 466: elationship between OSI and ISDN: t
Page 470: network and for networks to communi
Page 474: Copyright © 2002 by Marcel Dekker,
Page 478: shown in Fig. 8.1. Some of the attr
Page 482: It is possible to formulate a metho
Page 486: transmitting power. The smaller the
Page 490: FIGURE 8.12Tessellated clusters of
Page 496: FIGURE 8.14TCP=IP suite and its rel
Page 500: access to an Internet point of pres
Page 504: message security via satellite is d
Page 508: REFERENCES1. Wu, W.W. (1989). Eleme
Page 512: Appendix ANotationsThe symbols have
Page 516: N sPP rP sP TRRðtÞR cR eR rR vSS
Page 520: g Central anglez Channel gainZ Ante
Page 524: AttenuationBandwidthBearer serviceB
Page 528: Frequency divisionmultiple accessFr
Page 532: MultiplexingNetworkOmnidirectionala
Page 536: UplinkUser-to-networkinterfaceThe e
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