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ecause a voice signal is usually highly correlated. The filtering stages formpart of internal constructs of encoder=decoder units. Their function is tosuppress low-frequency noise and apply an anti-aliasing process to it.Various types of codecs are available, and their applications vary as thenetwork demands. However, the levels of programmability, the clock frequencies,and the fabrication technologies used dictate the difference. The codecalso coordinates the timing between itself and the network(s) with which itinterfaces. Data transmission is synchronized and multiplexed. To maintain theindustry standard of voice signal quality, the digitized voice signal must have asignal-to-distortion level of at least 30 dB over a 40-dB dynamic range [9]. Inorder to meet this specification, two methods of data reduction (companding)have been specified: m-law (also called Mu-255 law) and A-law.Companding, simply a compression and expansion process, is used toupgrade the quality of the pulse, which increases the signal-to-noise ratio andreduces peak power to prevent overloading. Both the encoder and decoderunits of the codec perform companding.The m-law companding technique is the standard used in North Americaand Japan, whereas the A-law companding technique is the accepted standardin Europe. Most codec manufacturers have developed a device that meets bothcompanding techniques. These laws are logarithmics:m-law:Y ¼lnð1 þ mjxjÞlnð1 þ mÞð3:45ÞwhereY ¼ Coding range.x ¼ Amplitude, 1 x 1.The value of m is determined by the law and is constant.A-law:Y ¼ 1 þ lnðAjxjÞ1; where jxj 11 þ lnðAÞA ð3:46ÞAxY ¼1 þ lnðAÞ ; where 0 jxj 1 Að3:47ÞThe value of A is determined by the law and is constant.The main difference between m-law and A-law is that in A-law thenormalized amplitude x is replaced with a signal whose amplitude is smallerCopyright © 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
Page 186: Small earth stations are antennas w
Page 190: FIGURE 3.2BPSK space diagram.Instea
Page 194: OQPSKOffset QPSK (OQPSK) is a modif
Page 198: FIGURE 3.7An 8-PSK space diagram.an
Page 202: aud. The word ‘‘baud’’ hono
Page 206: Noise power density N 0bandwidth:N
Page 210: We observe in (3.11) that E b =N 0
Page 214: to (3.23) shows that a margin of 11
Page 218: FIGURE 3.12 Principle of scrambling
Page 222: Equalization FilterAn equalization
Page 226: that is, N zeros at the top and bot
Page 230: Example 3.2: Consider a transmissio
Page 234: which can be written as89>=R xy ðt
Page 240: than 1=A. Whichever law is used, th
Page 244: FIGURE 3.16Block diagram for estima
Page 248: 3.4.2 Antenna TrackingAn earth stat
Page 252: controlling antenna pointing. The m
Page 256: FIGURE 3.19A generalized model of a
Page 260: FIGURE 3.20Entropy of a binary sour
Page 264: whereHðYÞ¼output entropy, the av
Page 268: To have a feel for this expression,
Page 272: 2. The system’s overall condition
Page 276: transmitted down the fiber as digit
Page 280: 10. Kantor, L. Y. (ed). (1987). Han
Page 284: 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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