Showing papers on "Quadrature amplitude modulation published in 1977"

Introduction to Communication Systems

Abstract: 1. Introduction. 2. Orthogonality and Signal Representations. Signals and Systems. Classification of Signals. Classification of Systems. Signals and Vectors. Orthogonal Functions. Choice of a Set of Orthogonal Functions. The Exponential Fourier Series. Complex Signals and Representations. The Trigonometric Fourier Series Representation. Extension by Periodicity. Parseval's Theorem for Power Signals. The Frequency Transfer Function. Steady-State Response to Periodic Signals. Harmonic Generation. The Fourier Spectrum and Examples. Numerical Computation of Fourier Coefficients. Effects of Alias Terms. Singularity Functions. Impulse Response. Convergence of the Fourier Series. Summary. Problems. 3. The Fourier Transform and Applications. Representation of an Aperiodic Function Over the Entire Real Line. The Spectral Density Function. Existence of the Fourier Transform. Parseval's Theorem for Energy Signals. Some Fourier Transforms Involving Impulse Functions. Properties of the Fourier Transform. Some Convolution Relationships. Graphic Interpretation of Convolution. Filter Characteristics of Linear Systems. Transversal Filters. Bandwidth of a System. Requirements for Distortionless Transmission. Time Response of Filters. Minimum Time-Bandwidth Product. The Sampling Theorem. Aliasing Effects in Sampling. The Discrete Fourier Transform. The Fast Fourier Transform. Summary. Problems. 4. Spectral Density and Correlation. Energy Spectral Density. Power Spectral Density. Time-Averaged Noise Representations. Correlation Functions. Some Properties of Correlation Functions. Correlation Function for Finite-Energy Signals. Band-Limited White Noise. Summary. Problems. 5. Amplitude Modulation. Amplitude Modulation: Suppressed Carrier. Amplitude Modulation: Large Carrier (AM). Frequency-Division Multiplexing (FDM). Single-Sideband (SSB) Modulation. Vestigial-Sideband (VSB) Modulation. A Time-Representation of Bandpass Noise. Signal-to-Noise Ratios in AM Reception. Propagation Effects. Comparison of Various AM Systems. Summary. Problems. 6. Angle Modulation. FM and PM. Narrowband FM. Wideband FM. Average Power in Angle-Modulated Waveforms. Phase Modulation. Generation of Wideband FM Signals. Demodulation of FM Signals. Signal-to-Noise Ratios in FM Reception. Threshold Effect in FM. Signal-to-Noise Improvement Using Deemphasis. Summary. Problems. 7. Pulse Modulation. Pulse-Amplitude Modulation (PAM). Time-Division Multiplexing (TDM). Pulse Shaping and Intersymbol Interference. Other Types of Analog Pulse Modulation: PWM and PPM. Signal-to-Noise Ratios in Analog Pulse Modulation. Pulse-Code Modulation (PCM). Fiber Optic Communication Systems. Use of Parity and Redundancy in PCM. Time-Division Multiplexing of PCM Signals. Integrated Services Digital Network (ISDN). The Matched Filter. Matched-Filter Codeword Detection. Pseudonoise (PN) Sequences. Summary. Problems. 8. Probability and Random Variables. Probability. Conditional Probability and Statistical Independence. The Random Variable and Cumulative Distribution Function. The Probability Density Function. Statistical Averages. Some Probability Distributions. The Histogram. Transformations of Random Variables. Joint and Conditional Density Functions. Correlation Between Random Variables. The Bivariate Gaussian Distribution. Random Processes. Autocorrelation and Power Spectra. Numerical Computation of Power Spectra. Summary. Problems. 9. Information and Digital Transmission. A Measure of Information. Channel Capacity. Ideal Demodulator Detection Gain. Quantization Noise. Probability of Error in Transmission. S/N Performance of PCM. Delta Modulation and DPCM. Error Analysis of PCM Repeaters. Power Spectral Densities of Data Waveforms. Partial-Response Signaling. Equalization. M-ary Signaling. Coding for Reliable Communication. Summary. Problems. 10. Digital Modulation. Amplitude-Shift Keying (ASK). Frequency-Shift Keying (FSK). Phase-Shift Keying (PSK). Comparison of Binary Digital Modulation Systems. Direct-Sequencing Spread Spectrum Systems. Quadrature AM (QAM) and Quaternary PSK (QPSK). Continuous-Phase FSK (CPFSK) and Minimum-Shift. Keying (MSK). M-ary Orthogonal FSK. Frequency-Hopping (FH) Spread Spectrum Systems. M-ary PSK. Amplitude-Phase Keying (APK). Comparison of Digital Modulation Systems. Representation of Digital Waveforms. Optimum Detection Algorithms. Summary. Problems. Appendix A: Selected Mathematical Tables. Appendix B: Decibels. Appendix C: Broadcast Frequency Bands. Appendix D: Commercial Television Transmission. Appendix E: Telephone Channels. Appendix F: Some Commercial Preemphasis/Deemphasis Systems. Appendix G: A Table of Bessel Functions. Appendix H: Stereo AM. Appendix I: A Table of Gaussian Probabilities. Index.

Fast start-up equalization with periodic training sequences

Abstract: Prior knowledge of the typical signal spectrum at the equalizer input can be used to speed up the convergence of a least mean-square error nonrecursivc equalizer by placing a weighting matrix in the path of the coefficient (tap gain) corrections. When the training sequence is periodic with period equal to the time-spread of the nonrecursive equalizer, the weighting matrix is not only symmetric and Toeplitz, but also circulant. Thus the fast update algorithm can be implemented by inserting a single nonrecursive filter in the path of the periodic input sequence before it is used for computing coefficient correction terms. The stability and convergence of the fast start-up algorithm with "stochastic" update in the presence of noise are examined. In the absence of prior information about the channel characteristics, this fast converging training procedure may be easily extended to a one-shot method of equalizer setup. The one-shot method, which involves estimation of the inverse filter from one period of the received signal, proves to be robust in the presence of noise. Simulation resuits are given for class I partial-response and Nyquist (20 percent roll-off raised cosine) data transmission systems with quadrature amplitude modulation over a dial-up telephone connection.

Optimal reception of digital data over the Gaussian channel with unknown delay and phase jitter

Abstract: Asymptotically optimum (in the sense of minimum per-symbol error rate) receiver structures for data communication over the white Gaussian channel with unknown time delay and carrier phase jitter are developed. The receiver structures apply to the following suppressed-carrier modulation systems: double sideband (DSB), quadrature amplitude modulation (QAM) with an arbitrary constellation, vestigial sideband (VSB) and single sideband. The resulting minimum error probability receivers are asymptotically equivalent to maximum-likelihood digital {\em sequence}-estimating receivers. The optimum structures implicitly derive joint maximum-likelihood estimates of the unknown parameters and of the sequence of data symbols. It is shown that the parameter estimates can be obtained from two data-directed stochastic approximation algorithms. Unlike traditional theoretical treatments of this communication situation, which have separated the highly important carrier phase and timing recovery problem from the detection problem, a unified theory is presented from which the complete ideal receiver structure can be deduced.

A Worst-Case Crosstatk Comparison Among Several Modulation Schemes

Abstract: The effects of worst-case crosstalk (from a time-domain point of view) on unsynchronized frequency division multiplexed (FDM) constant envelope modulations are considered assuming coherent hard-decision receivers and no filtering for bandwidth constraint. Continuous-phase frequency shift keying (FSK) is found to be superior to various forms of phase shift keying (PSK).

On Improving Bit Error Probability of QPSK and 4-Level Amplitude Modulation Systems by Convolutional Coding

Abstract: We consider Amplitude Modulation (AM) systems, PhaseShift-Keying (PSK) and Amplitude-Phase-Keying (APK) systems in which each symbol can take 2nvalues. After a systematic search of (n, n - 1) binary convolutional codes with large values of free distance and minimal number of code words at that distance, simulations have been performed with an 8-symbol modulation system ( n = 3 ). For a bit error probability of less 2 \times 10^{-4} , the saving in average power signal-signal-to-noise ratio over that required for an uncoded system with the same channel symbol rate was more than 2 dB with PSK and APK, and 1.5 dB with AM.

Transmission and reception system and its device of quadrature multiplex signal

Abstract: PURPOSE:To make the transmission of the high efficient PAM signal at almost equal rate to Nyquist rate, at the time of transmission by multi-plexing these after having converted to N pieces of the quadrature amplitude modulation signal, the base band PAM signal of 2N channel which is mutually cycled by the clock cycle T seconds by 2N pieces of carrier waves whose neighbouring carrier wave has the frequency difference of 1/T cycle and whose phase is set so that the respective carrier waves can be in phase or keep the quadrature relation.

The Effect of Carrier Phase Error on the Performance of a Duobinary Shaped QPSK Signal

Abstract: An analysis is presented showing the effect of carrier phase error on the error-rate of a duobinary shaped, quaternary, phaseshift keying digital radio system. A simple upper bound on the probability of error as a function of phase error is derived and the results are compared to those obtained by computer simulation. The conclusion is reached that such a system exhibits approximately 1.0 dB degradation for a carrier phase error of 3° at an error-rate of 10-5and a 10 dB degradation at a phase error of 15°.

Conversion of amplitude modulation to phase modulation

Abstract: The paper begins with a review of the work in the field of AM—PAI conversion by the injection synchronization technique. It presents a detailed theoretical investigation of the performance of such a system, and presents a now system of injection synchronization. Theoretical conclusions leading to the appropriate choice of the system parameters have been given.

A Broad-Band Impedance Indicator Employing a Phase-Shift Keying Modulator

Abstract: A novel homodyne scheme for implementing a broad-band impedance indicator is proposed. It features a simple form made possible by using a modified quarternary phase-shift keying as a subcarrier modulation method. This method allows both the amplitude and the phase of a signal to be detected simultaneously by one single-ended mixer. A prototype indicator has assured the swept-frequency measurement over the band ranging from 8.6 to 10.4 GHz with the amplitude and phase errors of less than 5 percent and 5°, respectively. The capabilities are demonstrated by presenting examples of measurement.

A review of delta modulation systems

Abstract: 355 to consider speech to be an all-pole process. This oversimplification of what is actually known about speech encourages belief that all-pole linear prediction can lead to an exact representation. The finite duration of individual glottal pubes and the antiresonance characteristics of the nasal tract prevent true representation and the reader should not be misled. As noted by the authors, there are current efforts at combined pole-zero estimation using linear prediction. However , the reader should not despair at this criticism of the current state of affairs: the chapters on applications illustrate the many productive uses of all-pole linear prediction for speech communication and parameterization. \" Automatic Formant Trajectory Estimation, \" \" Fundamental Frequency Estimation, \" and \" Vocoders \" are covered in the chapters with those titles. As elsewhere throughout the book, the discussion is accompanied by computer programs so that the reader may rapidly establish and use the techniques. As in the mathematical sections, the authors feature their own work and that of their-lose colleagues, but there is ample discussion of and reference to competing opinions and procedures. It should be noted that the power of linear prediction has not relieved one from the aforementioned reliance on special rules and heuristic procedures in processing speech. Up to this point in the review, only some, seemingly more important, topics from the total covered by the authors have been discussed. This raises the question of completeness which, if one is to follow the generalistic tone set in the first paragraph, should be answered for the area of linear prediction of speech, not just for the book. This can start with a game to see if the authors have identified all the different problem formulations leading to linear prediction , starting with Prony's work in 1795. In Chapter 2, \" Formulations, \" they cover a goodly number, taking the reader over minimum variance and maximum likelihood, time averages and ensemble averages, as well as correlation functions and Gaussian density functions.. However, they can be one-upped by citing Berg's work on entropy [ 1 ]. A review of the topic of linear prediction of speech identifies at least two areas which merit more attention: prediction of fixedduration frames with varying coefficients and prediction by continuously adaptive methods. Both areas converge to the consideration of continually changing coefficients. Liporace has developed the mathematical relationships for expressing the usual prediction coefficients as sums of …

Effect of emphasis on threshold in angle modulation systems

Abstract: Emphasis can be used in angle modulation systems (frequency and phase modulation) to improve receiver output signal-to-noise ratio (SNR). It is shown that the threshold input SNR increases when emphasis is used. The increase may be well over one decibel, depending on system parameters, when the message is Gaussian and random.