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OQPSKOffset QPSK (OQPSK) is a modified form of QPSK. The only differencebetween QPSK and OQPSK is the waveforms on the I- and Q-channels areshifted or offset in-phase from each other by T b =2, i.e., one-half of the bit time.Figure 3.5 shows an OQPSK block diagram and the bit alignment diagram.Because changes in the I-channel occur in the midpoints of the Q-channel bits,and vice versa, there is never more than a single bit change in the binary code.As a result, there is never more than a 90 shift in the output phase, which iscontrary to the conventional QPSK, where any change in the binary codecauses a corresponding 180 shift in the output phase. This phase shift must beimparted during the modulation process. The defect of this modulation schemeis that changes in the output phase only occur at twice the data rate in eitherchannel.3.2.3 8-QPSKWhen the index b ¼ 3; M ¼ 8, an 8-phase PSK is derived. With an 8-PSKmodulator, there are eight possible output phases, in which the phase of theFIGURE 3.5OQPSK modulator: (a) OQPSK block diagram; (b) bit sequence map.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
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 182: The most popular forms of modulatio
Page 186: Small earth stations are antennas w
Page 190: FIGURE 3.2BPSK space diagram.Instea
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
Page 232: FIGURE 3.14The three-tap equalizer
Page 236: First, in the case of digital signa
Page 240: 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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