`Systems, Modulation, and Noise
`
`Fourth Edition
`
`R. E. ZI1EMER
`University of Colorado at Colorado Springs
`
`W. H TRANTER
`University of Missouri—Rolla
`
`SAMSUNG 1029
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`JOHN WILEY & SONS,INC.
`New York ¢ Chichester ¢ Brisbane * Toronto « Singapore
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`SAMSUNG 1029
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`1
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`Cover designer: DesignHeads, Boston
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`Cover image: Andrea Way, Tidepool, 1988.
`Ink and pencil on paper, 36 x S14”
`Private collection
`Courtesy Brody’s Gallery, Washington DC
`
`Copyright © 1995 by John Wiley & Sons,Inc.
`Previously published by Houghton Mifflin Company.
`
`Reproductionortranslation of any part of this work beyond that permitted by Sections 107 and
`108 of the 1976 United States Copyright Act without the permission of the copyright owneris
`unlawful. Request for permission or further information should be addressed to the Permission
`Department, John Wiley & Sons,Inc.
`
`ISBN: 0.471 12496 6
`
`Printed in the Unites States of America
`109876543
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`2
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`
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`Contents
`
`6.1
`
`6.2
`
`6.3
`
`6.4
`
`6.5
`
`7.1
`
`7.2
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`7.3
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`7.4
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`7.5
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`7.6
`
`7.7
`
`8.1
`
`8.2
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`8.3
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`8.4
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`8.5
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`NOISE IN MODULATION SYSTEMS
`
`394
`
`395
`Signal-to-Noise Ratios
`Noise and Phase Errors in Coherent Systems
`Noise in Angle Modulation Systems
`414
`Thresholds and Threshold Extension in FM
`
`408
`
`424
`
`432
`
`Noise in Pulse Modulation
`Summary
`441
`Further Reading
`Problems
`443
`Computer Exercises
`
`443
`
`451
`
`BINARY DATA TRANSMISSION
`
`453
`
`455
`Baseband Data Transmission in White Gaussian Noise
`Binary Synchronous Data Transmission with Arbitrary Signal
`Shapes
`462
`Error Probabilities for Coherent Binary Signaling Schemes
`475
`Modulation Schemes Not Requiring Coherent References
`482
`Digital Signaling Through Bandlimited Channels
`Multipath Interference
`497
`Flat Fading Channels
`504
`Summary
`511
`Further Reading
`Problems
`515
`Computer Exercises
`
`515
`
`526
`
`491
`
`ADVANCED DATA COMMUNICATIONS TOPICS
`
`529
`
`529
`M-ary Data Communications Systems
`Bandwidth Efficiencies of Digital Modulation Formats
`Synchronization
`562
`Spread-Spectrum Communication Systems
`Satellite Communications
`580
`Summary
`594
`Further Reading
`Problems
`596
`Computer Exercises
`
`596
`
`601
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`570
`
`556
`
`
`
`3
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`
`
`548
`
`'
`
`Advanced Data Communications Topics
`
`Quadrature-Amplitude-Shift Keying (QASK)
`Another signaling scheme that allows multiple signals to be transmitted
`using quadrature carriers is quadrature-amplitude-shift keying (QASK), which is
`also referred to as quadrature-amplitude modulation (QAM). For example,
`M-QASKutilizes a signal structure similar to that of (8.32) but with the data
`sequences d, and d, each taking on VM different possible levels. Thus, for
`example, we represent the transmitted signal in an arbitrary signaling inter-
`val for 16-QASKas
`
`
`
`s(t) =\(2 (A; cos w,t + B, sin w,t), OSt=T, (8.43)
`
`2E,
`
`where A, and B, take on the possible values ta and +3a with equal prob-
`ability. A signal-space representation for 16-QASK is shown in Figure
`8.13(a), and the receiver structure is shown in Figure 8.13(b). The probability
`of symbolerror for 16-QASK can be shown to be
`
`Pr = 1 — [4P(C|) + $P(C[) + 4°(C| 1M]
`
`(8.44)
`
`where the probabilities P(C|1), P(C | II), and P(C| II) are given by
`
`;
`2a’
`|
`
`PCI) =|}1 — 2g] \/ (8.45a)
`.
`No
`
`
`
`2a! |
`P(C|II) = [ —2
`No
`e
`P(C|II) = [ - of al
`
`2a*\
`
`No
`
`1—
`
`@
`
`2a!
`No
`
`(8.45b)
`(8.450)
`
`|”
`
`is the average energy
`In the preceding equations a = E10, where E,
`per symbol. The notation I, II, or III denotes that the particular probability
`refers to the probability of correct reception for the three types of deci-
`sion regions shown in Figure 8.13(a). This error probability will be com-
`pared with that for M-ary PSK later. The error probability for 64-QASK
`or 256-QASK also can be obtained in a straightforward, but
`tedious,
`manner.
`
`
`
`4
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`
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`8.1 M-ary Data Communications Systems
`
`549
`
`FIGURE 8.13 Signal space and detector structure for 16-QASK.(a) Signal
`constellation and decision regions for 16-QASK.(b) Detector structure for 16-
`QASK. (Binary representations for signal points are Gray encoded.)
`
`ot)
`
`| |
`
`(Il)
`
`(Il)
`
`(ll)
`
`(Ill)
`
`||||
`
`—— Decision boundaries
`Roman numerals show decision region type
`
`(a)
`
`ot)
`logic
`
`y(t)
`
`Thresholds
`and
`. decision
`
`Decision
`
`(2 sinwt
`T;
`.
`(b)
`
`Note: yit) = s(t) + nit), where a(t) is white Gaussian noise.
`
`
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`5
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`