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the channel and reconstruct the source signal with an arbitrarily smallprobability of error ifHðX ÞT s> C cT cð6:3ÞThe parameter C c =T c is called the critical rate. When HðX Þ=T s ¼ C c =T c ,thesystem is said to be operating at the critical rate (at capacity). Fig. 5.8 (inChap. 5, Sec. 5.2) has demonstrated that operating a system at capacity isachievable only if the value of E b =N 0 is above the Shannon limit; that is,log e 2ð 1:6dBÞ. Recently, however, parallel-concatenated convolutional codeshave achieved a performance close to this theoretical limit [6] (more is said ofthe convolutional coding technique in Sec. 6.2.2). In general, the objective isto achieve maximum data transfer in a minimum bandwidth while maintainingan acceptable quality of transmission. To achieve this, an error-detecting codemust be devised. The most desirable solution is to use a forward errorcorrection (FEC) technique. Error detection coding is a technique foradding redundant (extra) bits to a data stream in such a way that an error inthe data stream can be detected [7].6.2 FORWARD ERROR CORRECTION CODINGTECHNIQUESForward error correction (FEC) techniques are widely used in control andtelecommunication systems. FEC codes may be divided into two broad types:linear block codes and convolutional codes.6.2.1 Linear Block CodesIn linear block codes, the encoder splits up (or maps) the incoming data streaminto blocks of k digits and processes each block individually by addingredundancy (extra digits) as a parity check according to a predefined algorithm.The output of the encoder is a codeword with n digits, where n > k. Thecode rate is also given by (6.1).The general form of a linear block codeword isY ¼ GXð6:4ÞCopyright © 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
Page 326: Follow the uplink procedure for the
Page 330: Satellite:Frequencies:14.75 GHz up
Page 334: 6. For link to be maintained betwee
Page 338: 5.1 PRINCIPLES OF MULTIPLE ACCESSAs
Page 342: neously, their transmissions collid
Page 346: technique and would remain the most
Page 350: FIGURE 5.4 Typical TDMA frame struc
Page 354: FIGURE 5.6TDMA throughput for an IN
Page 358: and transmits through the satellite
Page 362: FIGURE 5.8FDMA total capacity respo
Page 366: tion; that is, log e ð1 þ xÞ x t
Page 370: REFERENCES1. Spilker, J.J. (1977).
Page 374: 6.1 CHANNEL CODINGNoise within a tr
Page 380: message sequence X . Thus, a system
Page 384: If we consider a message X ¼ð1010
Page 388: can be seen in Table 6.1 that the m
Page 392: FIGURE 6.1A (7, 4) cyclic code gene
Page 396: FIGURE 6.2Convolutional codes encod
Page 400: Alternative methods of describing a
Page 404: FIGURE 6.5 Code tree diagram of Fig
Page 408: FIGURE 6.8 Code tree diagram of rat
Page 412: consistent with the constraint leng
Page 416: trellis depth is approximated to 5L
Page 420: FIGURE P.1A convolutional coder.the
Page 424: 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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