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access to an Internet point of presence via a gateway station for connection tothe satellite’s network access gateway (NAG). The NAG then sends themessage across the proximate backbone network of the recipient’s ISP,which is finally delivered to the intended recipient’s address. For this typeof application, channel capacity needs to be shared by different users.Subscribers’ access to satellite using a subscriber unit (e.g., handheld,pocket-sized phones) may be the simplest feature of satellite mobile systems ofthe future where the subscribers will be able to access voice, facsimile, data,and paging services with acceptable high quality.There are direct benefits for users accessing Internet via satellite,includingConnection through or bypassing terrestrial networks and provision fordirect-to-home services via the digital video broadcasting (DVB) IP.DVB technology uses multiplexing (e.g., MPEG-2) for data packetingbut with different channel modulation. MPEG-2 is the broadcastqualitycompression standard for video communication.Provision for higher throughput and possibly asymmetric links.Allowance for multicasting transmission; that is, sending one message toauthorized users instantaneously within the network through a varietyof earth stations.Provision for faster access (or response) time and delivery of informationto any inhospitable terrain or region where there is rapidlyexpanding customer demand but insufficient terrestrial infrastructure.Of course, there have been attempts to deliver IP via satellite, but the satellitetechnologies have focused on connection-oriented transmission protocols,which are really suited for voice traffic rather than IP, unnecessarily squanderingexpensive capacity. What are the challenges ahead for effective delivery ofIP via satellite?8.3.3 Technical ChallengesThe TCP=IP shortcomings in the typical satellite environment include latency(degradations due to slow-start), data security over the satellite link, andoptimization (window size, traffic acknowledgment for short transmissionsover high-latency channels, as well as scheduling capacity). These shortcomingsdemand attention in order to provide more efficient, secure, andapplication-expansive internetworking via satellite. The issue of data orCopyright © 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
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8Mobile Satellite System Services8.
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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 494: 8.3.1 The InternetThe Internet cons
Page 498: SecurityData security is a matter o
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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