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Communications, IEEE Transactions on

Issue 1 • Date January 1974

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Displaying Results 1 - 18 of 18
  • [Front cover and table of contents]

    Publication Year: 1974 , Page(s): 0
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    Freely Available from IEEE
  • Communication Systems Design - P. Panter [Book Reviews]

    Publication Year: 1974 , Page(s): 95 - 96
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    Freely Available from IEEE
  • [Back cover]

    Publication Year: 1974 , Page(s): 0
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    Freely Available from IEEE
  • Quantized Feedback in an Experimental 280-Mb/s Digital Repeater for Coaxial Transmission

    Publication Year: 1974 , Page(s): 1 - 5
    Cited by:  Papers (13)  |  Patents (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (576 KB)  

    A 280-Mb/s digital coaxial repeater employing two-level transmission with quantized feedback for dc-wander control has been designed and constructed. The linear channel forward path includes a 10-MHz low-frequency cutoff, and the missing low frequencies are supplied by a filtered signal from the repeater output. This approach effectively removes dc wander without use of code restriction, making it possible to use two-level rather than three-level transmission without loss of information transmission. Eye margins are consequently significantly greater than for previously designed 280-Mb/s three-level repeaters. The bandwidth ratio, or ratio of upper to lower 3-dB down points of the signal transmission path, is only 10 for this approach compared to several hundred for the three-level bipolar approach (and more for codes with higher transmission efficiency). This results in greatly reduced susceptibility to interference from lightning and power surges, elimination of preamplifier overload, and simplified repeater design. View full abstract»

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  • Direct-Detection Optical Communication Receivers

    Publication Year: 1974 , Page(s): 17 - 27
    Cited by:  Papers (19)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1184 KB)  

    A model that is sufficiently general to describe the predominant statistical characteristics of the output of many real optical detectors is formulated. This model is used to study the optimum receiver processing for direct-detection optical communication systems. In particular, the structures of detectors and estimators for randomly filtered doubly stochastic Poisson processes observed in additive white Gaussian noise are considered. Representations for the posterior statistics of a vector-valued Markov process that modulates the intensity of the doubly stochastic Poisson process are obtained. Quasi-optimum estimators and detectors are specified in general terms and specialized for several important applications. These include a demodulator for subcarrier angle modulation, a detector structure for binary signaling with known intensities, and a detector structure for binary signaling in the turbulent atmosphere. View full abstract»

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  • Digital Companding Techniques

    Publication Year: 1974 , Page(s): 75 - 78
    Cited by:  Papers (4)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (472 KB)  

    This paper deals with the requirements for the design of digital companding techniques in either delta or pulse-code modulation. Both delta and pulse-code modulation convert analogue signals into binary signals and in both these systems the dynamic range is normally small. By the use of companding, the dynamic range can be extended. Since both delta and pulse-code modulation are digital methods, they are well suited to the use of digital companding techniques. The binary transmitted signal normally contains a measure of the system performance. By observing certain patterns in this binary signal and using the occurrence or nonoccurrence of these patterns to change the gain of the modulator and demodulator, syllabic companding can be obtained. The selection of the binary pattern and the rate of change of gain of the modulator and demodulator, determines both the point at which the companding operates and the attack and decay times. The ratio of the largest to the smallest value of the gain determines the dynamic range. By the use of digital circuitry, the gain can be controlled with sufficient accuracy over a large dynamic range. The paper deals with the principles involved in selecting the binary patterns to control the gain of the modulator and as examples a delta modulation system and a pulse-code modulation system with companding ratios of 60 dB are discussed. View full abstract»

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  • Bit Error Probability for Baseband and Subcarrier Optical Communication Systems

    Publication Year: 1974 , Page(s): 55 - 62
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (648 KB)  

    Digital baseband and digital subcarrier noncoherent optical communication systems are considered in this paper. Expressions are developed for the bit error probability of optical subcarrier systems which use a nonliner polarization modulator and either a one-detector or a two-detector receiver, The expressions are evaluated numerically, and the results are used to compare the one- and two-detector subcarrier systems with the corresponding one- and two-detector baseband systems for a fLxed bit error probability. View full abstract»

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  • Spectrum Clipping

    Publication Year: 1974 , Page(s): 38 - 45
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    A new signal-processing technique, spectrum clipping, has been investigated. The spectrum clipper is a passive two-port nonlinear circuit that employs parametric excitation of vibrational modes in a magnetoelastic crystal. Spectrum clipping can be considered as a means of recovering periodic and nearly periodic signals from noise. signal-to-noise ratio (SNR) improvements of up to 30 dB are predicted, the largest improvement occuring for simple sinusoidal signals. Preliminary theoretical and experimental results suggest that spectrum clipping may conceivably provide a low-cost method of interference reduction for domestic communications systems. View full abstract»

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  • An Economical Hardware Realization of a Digital Linear Predictive Speech Synthesizer

    Publication Year: 1974 , Page(s): 82 - 88
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (784 KB)  

    Speech analysis/synthesis algorithms utilizing linear prediction coefficients have certain advantages over those employing formantbased techniques. For example, 4-kHz speech samples may be synthesized using a basic sequence of 10 multiply/adds followed by a single addition of the current sample of the excitation function. Real-time software synthesis of 4-kHz speech is possible (using this technique) on certain 16-b minicomputers, but the central processing unit (CPU) overhead may approach 100 percent. We describe an economical (< 600-dollar) hardware realization of a 4-kHz digital linear predictive speech synthesizer which requires, at most, a CPU overhead of about 40 percent real time. The device is constructed of standard TTL/MOS logic and consists (essentially) of a high speed 2's complement multiplier/adder capable of calculating a 26-b product (10-b speech samples, 16-b coefficients) in 0.33 μs, and a dual shift register. In addition, a procedure is discussed which enables the device to be used both as a formant synthesizer for vowels or voiced consonant production, and as a predictive synthesizer for other speech sounds. This procedure, hybrid synthesis, permits the utilization of formant concatenation techniques and reduces the coefficient storage required to specify vowels/voiced consonants by about 60 percent. View full abstract»

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  • A Second-Order All-Digital Phase-Locked Loop

    Publication Year: 1974 , Page(s): 62 - 68
    Cited by:  Papers (7)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (784 KB)  

    A simple second-order digital phase-locked loop has been designed to synchronize itself to a square-wave subcarrier. Analysis and experimental performance are given for both acquisition behavior and steady-state phase error performance. In addition, the damping factor and the noise bandwidth are derived analytically. Although all the data are given for the square-wave subcarrier case, the results are applicable to arbitrary subcarriers that are odd symmetric about their transition region. View full abstract»

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  • Coupling Errors in Ground Vehicle Communication Systems

    Publication Year: 1974 , Page(s): 45 - 54
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (904 KB)  

    Communication systems for high-speed ground vehicles which employ coupled surface waveguides are considered in this paper. We determine communication errors resulting from AM and FM transmission for the coupling configuration of two randomly separated Goubau lines as a function of the various system parameters. Results are given which indicate that filtering of the transmitted and received signals leads to enhanced communications. View full abstract»

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  • Transient Mean and Variance of Phase Error of the First-Order Phase-Locked Loop

    Publication Year: 1974 , Page(s): 78 - 82
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (512 KB)  

    Based on the Fokker-Planck techniques, the time-dependent mean and variance of phase error of the first-order phase-locked loop in the presence of white Gaussian noise have been obtained via stochastic differential equations. The steady-state variance reduced from the transient case is simple in its form and agrees closely with the previous results obtained by different approaches. View full abstract»

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  • Hybrid Decoding of Bipolar Signals

    Publication Year: 1974 , Page(s): 88 - 93
    Cited by:  Patents (1)
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    An analog-digital hybrid decoder which combines amplitude and duration threshold detection and bipolar violation sensing capabilities for decoding bipolar signals is described. The main features of the decoder are: 1) a preamplifier with automatic gain control (AGC), 2) amplitude and duration threshold detectors, 3) a bipolar violation sensor, and 4) a unipolar pulse generator. The decoder is extremely robust and is self-synchronizing. If, during operation, burst errors occur, introducing bipolar violations in the received signal, the decoder decides that, where a violation has occurred, a binary "0" was transmitted. If, for some reason, the decoder is perturbed from its synchronous condition, it requires at most 1-b duration to reacquire synchronization. That is, the decoded message contains at most one erroneous bit. View full abstract»

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  • Quantizing and Sampling Considerations in Digital Phased-Locked Loops

    Publication Year: 1974 , Page(s): 68 - 72
    Cited by:  Papers (6)
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    Quantization and sampling effects on the digital phasedlocked loop (DPLL) structures obtained for demodulation of anglemodulated signals using extended Kalman filter algorithms are investigated for the high signal-to-noise ratio (SNR) case in this paper. First, the problem of quantization is considered. The validity of the uniform white sequence model for quantizer error in the DPLL is established independent of the sampling rate. Simulation results are presented for several quantizer word lengths. Also, an effective SNR is defined which allows prediction of quantized performance from unquantized results. Secondly, minimum sampling requirements for the DPLL are considered. The effect of sampling rate variation upon the predicted phase error covariance is examined. Again, simulation results are presented and compared to the predicted phase error covariance values. This results in an analytical method for determining minimum sampling rates for the DPLL. Minimum sampling rates for quantized DPLL have also been determined using the effective SNR previously defined. View full abstract»

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  • Feedback Communications in Fading Channels

    Publication Year: 1974 , Page(s): 93 - 95
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (288 KB)  

    A modulation scheme for varying the data rate and transmitted power in accordance with received signal strengths in a fading channel is discussed. The system, using ideal feedback, performs better than one using only rate control with the same constraint on bandwidth. View full abstract»

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  • An Error-Probability Upper Bound for Coherent Phase-Shift Keying with Peak-Limited Interference

    Publication Year: 1974 , Page(s): 6 - 16
    Cited by:  Papers (24)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1144 KB)  

    An upper bound on the probability of error for coherent phase-shift-keyed (CPSK) systems operating in the presence of peaklimited interference is derived. Such a bound is particularly useful in analyzing the effect of co-channel and adjacent channel interference on CPSK systems. The bound is often tight enough to be employed as a system design tool, and is computationally simple to apply. View full abstract»

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  • Optimization of Two-Dimensional Signal Constellations in the Presence of Gaussian Noise

    Publication Year: 1974 , Page(s): 28 - 38
    Cited by:  Papers (106)  |  Patents (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (960 KB)  

    A considerable amount of literature exists on the problem of selecting an efficient set of N digital signals with in-phase and quadrature components for use in a suppressed carrier data transmission system. However, the signal constellation which minimizes the probability of error in Gaussian noise, under an average power constraint, has not been determined when the number of signals is greater than two. In this paper an asymptotic (large signal-to-noise ratio) expression, of the minimum distance type, is derived for the error rate. Using this expression, a gradient-search procedure, which is initiated from several randomly chosen N -point arrays, converges in each case to a locally optimum constellation. The algorithm incorporates a radial contraction technique to meet the average signal power constraint. The best solutions are described for several values of N and compared with well-known signal formats. As an example, the best locally optimum 16-point constellation shows an advantage of about 0.5 dB in signal-signal-to-noise ratio over quadrature amplitude modulation. The locally optimum constellations are the vertices of a trellis of (almost) equilateral triangles. As N \rightarrow \infty , it is rigorously proved in the Appendix that the optimum constellations tend toward an equilateral structure, and become uniformly distributed in a circle. View full abstract»

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  • Exact Dynamics of Automatic Gain Control

    Publication Year: 1974 , Page(s): 72 - 75
    Cited by:  Papers (20)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (472 KB)  

    The exact input-output relationship is derived for a firstorder automatic gain control loop wherein the variable gain is an exponential function of the gain control voltage. The exact solution is compared to the linearized solution, and the condition for valid linearization is given. View full abstract»

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Aims & Scope

IEEE Transactions on Communications focuses on all telecommunications including telephone, telegraphy, facsimile, and point-to-point television by electromagnetic propagation.

 

 

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Editor-in-Chief
Robert Schober
University of British Columbia