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For an uncoded message x and the feedback function F, the encryptedmessage z can be written asz ¼½x zFŠGðK i Þð1:14ÞRearranging (1.14) in terms of z, wehavez½1 FGðK i ÞŠ¼xGðK i Þð1:15aÞorz ¼GðK iÞ1 FGðK i Þ x ð1:15bÞFor the decryption circuit, the expression for the decrypted message x can bewritten asx ¼½z xFŠGðK j Þð1:16aÞAlternatively, in terms of encrypted message z,z ¼ 1 FGðK jÞxGðK j Þð1:16bÞFor the same transmission sequence, (1.15b) and (1.16b) must be equal; thatis,1 FGðK j Þ¼GðK iÞGðK j Þ 1 FGðK i Þð1:17Þwhich turns toGðK i Þ¼1 FGðK j ÞGðK j Þ¼1 FGðK i Þð1:18ÞIt can be seen in (1.18) that the key functions relate to the feedback functions.If for argument’s sake we let the feedback F equate unity, then the keyfunctions become an additive inverse of each other. This shows that thefeedback function and the mapping function are linear functions in this type ofciphering. In general, a feedback mechanism enhances the strength of acryptosystem [7].1.5 SUMMARYThis chapter has briefly introduced the genesis and characteristic features ofcommunication satellites. A communication satellite is basically an electronicCopyright © 2002 by Marcel Dekker, Inc. All Rights Reserved.
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SatelliteCommunicationEngineeringMi
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This book is dedicated to my famili
Page 10: Because of the immense importance o
Page 14: means of a combination of applicati
Page 18: about my promise to my students, an
Page 22: 2.3 Coverage Area and Satellite Net
Page 26: 1Basic Principles of SatelliteCommu
Page 30: and voice (telephone) communication
Page 34: FIGURE 1.2Communication between two
Page 38: interpreting or uncovering the deci
Page 42: cryptographic keys K ti (where i ¼
Page 46: FIGURE 1.6Block ciphering technique
Page 50: FIGURE 1.7Part of block ciphering w
Page 54: Based on the ordering sequence of (
Page 58: TABLE 1.1 (continued )S612 1 10 15
Page 64: communication package placed in orb
Page 68: 2Satellites2.1 OVERVIEWA satellite
Page 72: stable over their operating tempera
Page 76: FIGURE 2.3 Geometric properties of
Page 80: at the altitudes of satellites, the
Page 84: whereg ¼ acceleration due to gravi
Page 88: 2.3 COVERAGE AREA AND SATELLITENETW
Page 92: The apex angle required at the sate
Page 96: the frontline satellites is then pa
Page 100: station antenna must be pointed to
Page 104: and the azimuth angle is a z ¼ 180
Page 108: 2.5.3 Swath WidthThe width of the v
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2.6.3 System Speci¢cations: Analys
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Like all materials that require cou
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By the first definition, the system
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SolutionFrom (2.28), we can estimat
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FIGURE 2.11An example of redundancy
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adiators. An antenna array is a fam
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Example 2.3: The earth subtends an
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eam is assumed symmetrical (i.e., y
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FIGURE 2.15Feed array elements ðy
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If the steering is in the direction
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2.8 SATELLITE POWER SYSTEMSA key co
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Calculate (1) the probability that
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FIGURE 2.20Carrier processing.infor
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FIGURE 2.22(d) elliptic.Types of ba
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FIGURE 2.23A klystron. (Courtesy of
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FIGURE 2.25A simple block diagram o
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tional protection is required to en
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3.1 BASIC PRINCIPLE OF EARTH STATIO
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3.1.1 Technical and Operational Req
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excellent protection against noise
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FIGURE 3.3QPSK modulator.FIGURE 3.4
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TABLE 3.28-PSK Truth TableInput bit
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FIGURE 3.8An M-ary PSK demodulator
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where B is the allocated channel ba
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A frequently used function is the Q
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In view of (3.11), Eq. (3.18) can b
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Encoder and DecoderAn encoder is an
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Modulator and DemodulatorA modulato
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Zero Forcing Technique. Suppose the
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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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