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3.1 BASIC PRINCIPLE OF EARTH STATIONSThe basic configuration of an earth station is shown in Fig. 3.1. An earthstation comprises an antenna, tracking system, receiver, transmitter, multiplexer(combiner), and terrestrial links via a modem (or codec).Conceptually, the internal electronic signals processing of an earthstation is quite simple. For example, let’s consider the processing of basebandsignals to form the transmitting signals of the earth station. The basebandsignals—such as video (TV), voice (telephone), and data—from users arebrought via the terrestrial link (e.g., optical fiber, twisted pair cable, coaxialcable, microwave link) from different sources. The baseband signals are thencombined (multiplexed)—and encoded with a forward error correction (FEC)scheme in the case of digital satellite communications—and modulated ontothe intermediate frequency (IF) carrier to form the earth station’s transmission.The transmission can be formatted as a single carrier or multiple contiguouscarriers. If the information from a single source is placed on a carrier, theformat is called single channel per carrier (SCPC). A distinction should bemade between a signal and a carrier. A carrier is an electromagnetic wave offixed amplitude, phase, and frequency that, when modulated by a signal, canbe used to convey information through a communication system. Themodulated signal can be analog or digital originating from a source, such astelephone, video (TV), data, and so on, and is often referred to as ‘‘modulatingthe carrier.’’ The complete set of these carriers is then radiofrequencytranslatedfor high-power amplification and transmission.If a satellite operates digitally, then analog signals must be converted todigital format before transmission. The conversion is done with a circuit calleda codec: a contraction of code and decode (more is said of codec in Sec. 3.3.2).FIGURE 3.1Block diagram of an earth station.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
Page 130: 2.7 ANTENNASBased on function, sate
Page 134: Two kinds of horns in common use ar
Page 138: FIGURE 2.13Geometry of a parabolic
Page 142: FIGURE 2.14 Axisymmetric reflector
Page 146: A transceiver antenna is a single a
Page 150: The gain, in the axial mode, of a h
Page 154: angles, spacecraft may shadow the s
Page 158: 3. The probability of both parallel
Page 162: the baseband signal (more details a
Page 166: matrix in the communications subsys
Page 170: FIGURE 2.24Typical transfer charact
Page 174: 4. Iridium LCC (1997). Iridium Syst
Page 178: 3Earth StationsIn Chap. 2 we discus
Page 184: 3.1.1 Technical and Operational Req
Page 188: excellent protection against noise
Page 192: FIGURE 3.3QPSK modulator.FIGURE 3.4
Page 196: TABLE 3.28-PSK Truth TableInput bit
Page 200: FIGURE 3.8An M-ary PSK demodulator
Page 204: where B is the allocated channel ba
Page 208: A frequently used function is the Q
Page 212: In view of (3.11), Eq. (3.18) can b
Page 216: Encoder and DecoderAn encoder is an
Page 220: Modulator and DemodulatorA modulato
Page 224: Zero Forcing Technique. Suppose the
Page 228: The adjoint of matrix A is obtained
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FIGURE 3.14The three-tap equalizer
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First, in the case of digital signa
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than 1=A. Whichever law is used, th
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FIGURE 3.16Block diagram for estima
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3.4.2 Antenna TrackingAn earth stat
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controlling antenna pointing. The m
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FIGURE 3.19A generalized model of a
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FIGURE 3.20Entropy of a binary sour
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whereHðYÞ¼output entropy, the av
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To have a feel for this expression,
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2. The system’s overall condition
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transmitted down the fiber as digit
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10. Kantor, L. Y. (ed). (1987). Han
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142. Simulate the probability of bi
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FIGURE 4.1A simplex link.baseband c
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Chapter 2, Sec. 2.7, discusses that
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From (4.6), the received power P r
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FIGURE 4.3A model of the combined-l
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4.1.2 Rain AttenuationRain attenuat
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FIGURE 4.5rates.Average rainstorm p
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FIGURE 4.6Adjacent satellite interf
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FIGURE 4.8Satellite separation dist
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inability of satellite A to accurat
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FIGURE 4.10 Cross-link E b =N 0 vs.
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Then using (4.41), the overall C=N
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(iv)(v)(vi)(vii)Calculate the recei
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5Communication Networks andSystemsC
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discriminate among carriers by temp
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FIGURE 5.2 Principle of FDMA system
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FIGURE 5.3 Operational concept of T
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FIGURE 5.5TDMA: bit rate r b for 1
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Copyright © 2002 by Marcel Dekker,
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5.2 CAPACITY COMPARISON OFMULTIPLE-
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Rearranging (5.11) in terms of ener
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The transmission bit rate isR r ¼
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6Error Detection and CorrectionCodi
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the channel and reconstruct the sou
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message sequence X . Thus, a system
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If we consider a message X ¼ð1010
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can be seen in Table 6.1 that the m
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FIGURE 6.1A (7, 4) cyclic code gene
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FIGURE 6.2Convolutional codes encod
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Alternative methods of describing a
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FIGURE 6.5 Code tree diagram of Fig
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FIGURE 6.8 Code tree diagram of rat
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consistent with the constraint leng
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trellis depth is approximated to 5L
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FIGURE P.1A convolutional coder.the
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7Regulatory Agencies andProceduresT
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of the radiofrequency spectrum, and
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The CCIR works through the medium o
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7.1.3 IFRBThe International Frequen
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The national or regional spectrum m
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3. The need to expand or enhance th
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The DSP will be responsible for res
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2. Provide a convenient framework w
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FIGURE 8.3Types of user-to-network
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H1-channels are designed to carry v
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information. The transfer cell prov
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The OSI layers are divided into two
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plane is denoted by U, the control
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interfacing, maintenance, and conne
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adjoining base station to scan the
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FIGURE 8.9Geometry of a polygon.The
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FIGURE 8.11Splitting cells into sma
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causes signal fading. Of course, th
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FIGURE 8.14TCP=IP suite and its rel
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access to an Internet point of pres
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message security via satellite is d
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REFERENCES1. Wu, W.W. (1989). Eleme
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Appendix ANotationsThe symbols have
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N sPP rP sP TRRðtÞR cR eR rR vSS
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g Central anglez Channel gainZ Ante
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AttenuationBandwidthBearer serviceB
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Frequency divisionmultiple accessFr
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MultiplexingNetworkOmnidirectionala
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UplinkUser-to-networkinterfaceThe e
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