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Communications, IEEE Transactions on

Issue 5 • Date October 1972

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Displaying Results 1 - 25 of 42
  • [Front cover and table of contents]

    Publication Year: 1972 , Page(s): 0
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    Freely Available from IEEE
  • Comments On "Testing a Sample Population for the Rayleigh Distribution" and a Succeeding Correction

    Publication Year: 1972 , Page(s): 1031 - 1032
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (193 KB)  

    In a recent correction [2] to previous correspondence [1] it was stated that 3) of the theorem in [1] was invalid due to the statistical dependence of the yi. The joint distribution function of the yiis derived below confirming their dependence, but also upholding the validity of Item 3. Furthermore, an exact goodness of fit test for the Rayleigh distribution based upon the N + 1 observations x_{1}, ... , x_{N+1} is suggested. View full abstract»

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  • Introduction to Signal Transmission

    Publication Year: 1972 , Page(s): 1046 - 1047
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    Freely Available from IEEE
  • [Back cover]

    Publication Year: 1972 , Page(s): 0
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    Freely Available from IEEE
  • A Semicycle of Ground-Potential Rise

    Publication Year: 1972 , Page(s): 929 - 935
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    A brief description is presented of why the power utilities need communication during faults. Wire communication channels can supply this need when suitably protected. The maximum groundpotential rise is needed to select protective equipment. How this transient voltage is generated with its wave shape and duration is explained for a single phase-to-ground fault on a power system. The peak occurs at about one-half cycle time at power frequency following a fault at the critical moment, with a magnitude determined by the X to R ratio. A possibility exists that an even higher voltage results when a phase-to-ground fault changes to a two-phase-to-ground fault after about frac{1}{3} cycle delay. View full abstract»

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  • Bandwidth Reduction Via Movement Compensation on a Model of the Random Video Process

    Publication Year: 1972 , Page(s): 960 - 965
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (680 KB)  

    The video-signal bandwidth reduction obtained by interframe differential transmission is hindered by rapid movements of the objects and the camera. A simple movement compensation procedure can be obtained by dividing the image into zones and then transmitting for each zone a displacement vector relating the zone to a zone in the previous flame that is maximally correlated with it. The effectiveness of such a procedure is studied on a model of the random video process, obtained as a derivation of a three-dimensional telegraph signal. In particular, it is shown that for this model, the optimal procedure for finding the most correlated zone in the previous frame is the one matching the intersections of the contour lines. The optimal size of the zone for which a single displacement vector has to be transmitted is also determined. View full abstract»

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  • Circuit for Impulse Testing of Gas-Tube Lightning Arresters

    Publication Year: 1972 , Page(s): 936 - 941
    Cited by:  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (680 KB)  

    Telephone lines may be protected from lightning-induced surges by gas-tube lightning arresters. Typical arresters break down at 250-400 V dc. Breakdown voltage increases with the rate of rise of the applied voltage and may be two or three times the dc value at a rate of rise of 10 kV/μs. Lightning surges on telephone lines approach this rate of rise. The circuit described in this paper generates and measures ramps with linear rates of rise from 0.5 to 10 kV/μs chopped at 500-1500 V. In order to achieve ramp linearity and to minimize oscillations after the chop, stray capacitances and inductances must be made as small as possible. Construction and layout required to achieve this are described in some detail and typical test oscillograms at 0.5 and 10 kV/μs are presented in corroboration. Measurement accuracy is analyzed and maximum errors are estimated to be, for breakdown voltage, 3 and 10 percent at 0.5 and 10 kV/μs, respectively; and for rate of rise, 5 percent for all ramps. If greater accuracy is required, it can be obtained by correction for divider time constant errors and by further study of carbon resistor voltage coefficients. View full abstract»

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  • Conference Nonblocking Switching Networks

    Publication Year: 1972 , Page(s): 942 - 946
    Cited by:  Papers (1)
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    Conferencing in three-stage nonblocking switching networks is investigated. Clos's results are extended to consider networks in which conference connections are made at the cross points rather than through the use of separate conference bridges. If conferencing is allowed only in the center stage, it is shown that the cross-point count is multiplied by approximately k/2 , where k is the number of conferees (for normal calls, k = 2 ). If conferencing is allowed in all stages, then it is shown that the Clos nonblocking network is conference nonblocking for arbitrarily large conferences. Similar results for Bowers' folded networks are also presented. View full abstract»

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  • Waiting-Time Distributions and Buffer Overflow in Priority Queueing Systems

    Publication Year: 1972 , Page(s): 865 - 877
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1288 KB)  

    This paper presents a numerical technique for the solution of a class of queueing problems having fixed priority assignment, synchronous service, constant service time, and finite number of sources. The analysis yields waiting-time distributions, namely, the probabilities of waiting exactly nW service cycles or longer. It applies to scanners, multiplexer channels, loop configurations, etc. It is especially useful for worst case design in that it permits the calculation of overflow probabilities. Results are given in the form of curves and are compared with those for exponential service times. A priority scheme is outlined that allows partial elimination of the geometrical priorities inherent to loop multiplexers. View full abstract»

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  • Phase Slipping in Phase-Locked Loop Configurations That Track Biphase or Quadriphase Modulated Carriers

    Publication Year: 1972 , Page(s): 984 - 991
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (536 KB)  

    The phase-slipping behavior of second-order squaring and quadrupling phase-locked loop configurations is investigated by digital computer simulation. Statistics are obtained for the mean time between batches of phase slips and the duration of the batches, as a function of the effective loop signal-to-noise ratio (SNR). View full abstract»

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  • Differential PCM for Speech and Data Signals

    Publication Year: 1972 , Page(s): 900 - 912
    Cited by:  Papers (35)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1072 KB)  

    The performance of differential PCM encoders used for both speech and data signals is investigated. Primarily concerned with data signals, this paper shows how differential PCM systems designed for speech perform with differential-phase-modulation, single sideband and partial response data signals operating at data rates of 1200-9600 bits/s. The seven signals considered in this study are shown in Table I. Also discussed are compromise differential PCM systems, which operate well for either speech or data but which are not optimum for either. These results show the advantages and limitations of using differential PCM on switched telecommunication networks carrying speech and data. This paper contains results generated by theoretical studies, computer simulation, and experiments with hardware encoders and modems. View full abstract»

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  • Special Issues, Page Charges, and a Dues Increase

    Publication Year: 1972 , Page(s): 835
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (75 KB)  

    First Page of the Article
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  • Timing Extraction in Baseband Pulse Transmission

    Publication Year: 1972 , Page(s): 877 - 884
    Cited by:  Papers (17)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (832 KB)  

    Timing extraction through nonlinearity in the presence of pulse overlaps is studied for baseband PCM or PAM systems. It is shown that the systematic jitter can be reduced by proper choices of nonlinearity, coding scheme, and pulse waveform. Discussions on choice of nonlinearity indicate that square-law rectification is desirable for elimination of jitter sources. This nonlinearity derives a frequency-domain expression for amplitude and phase of the timing wave that separates the effects of pulse pattern and pulse shapes and provides insight to their contributions to timing jitter. Proper choices of coding scheme and pulse waveform reduce amplitude and phase variation in the timing wave. For example, an optimum prefiltering (or correlative coding) reduces amplitude variation to one eighth for bipolar sequence. In the case of symmetrical reshaping by a Bessel (flat delay) filter, the maximum jitter exceeds 20 degrees if the order of a filter is less than ten. An asymmetrical reshaping makes the maximum jitter less than four degrees for the same order of filter. Some features of nonlinearities that approximate square-law rectification are discussed. View full abstract»

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  • Automatic Acquisition and Tracking System for Laser Communication

    Publication Year: 1972 , Page(s): 847 - 851
    Cited by:  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (640 KB)  

    A laser communication system, which has an automatic acquisition and tracking capability without the aid of any other communication link, has been constructed and experimented. It consists of two terminals that can transmit one TV signal and error signals for tracking each other. The heart of this system is a combination of a laser, a position sensor, an angle detector, and an optical deflector that can send back a laser beam parallel to an incident beam as if it were a retroreflector. The availability of this system was proved from a transmission experiment at the distance of 500 m. The maximum propagation distance of this system is estimated to be 1 km if a 200-mm diameter receiving aperture is used, even though there are spot dancing and beam spreads. View full abstract»

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  • Message Propagation Through Random Communication Networks

    Publication Year: 1972 , Page(s): 946 - 952
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    This study considers the message propagation problem in a "net-alert" situation through directed and undirected random networks having n nodes and probability of connection between the distinct pairs of nodes equal to p . The solution has been obtained by analyzing the structure of the random networks in terms of the probability distribution of the number of contacted new nodes, which are separated from the originator(s) of the message by simple chain progressions of k links. From these probability distributions, the average message propagation, the weak connectivity, and the k th terminal reliability are obtained. To aid the computation of these quantities first-order difference equations that approximate the average message propagation, the weak connectivity, and the k th terminal reliability are given. The application of the results is shown for random networks having several values of n and p . View full abstract»

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  • Decision Hysteresis Reduces Digital Pe

    Publication Year: 1972 , Page(s): 1038 - 1041
    Cited by:  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (392 KB)  

    It is shown that the source statistics influence the form of the decision threshold in an optimum receiver. For a first-order Markov source, a simple suboptimum realization is a hysteresis loop. The performance improvement over the single threshold decision rule is modest but in some cases it is possible to cut the Pein half. One case where decision hysteresis performs best is in a modem that uses split phase or data scrambling to ensure that the transmitted signal tends to alternate. As a practical matter, it turns out that hysteresis can do more damage than good if the signal-to-noise ratio is variable. View full abstract»

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  • Statistical Word Synchronization in PCM Transmission of TV Signals

    Publication Year: 1972 , Page(s): 995 - 998
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    Word synchronization in PCM of TV signals is more important than that of audio signals, since often a single channel of TV signals is transmitted independently. For this purpose, new word synchronization is proposed, where the statistical property of TV signals is utilized instead of adding a bit for synchronization. The property is that a more significant bit in PCM does not change word by word as frequently as a less significant bit, because of the correlation between adjacent picture elements, i.e., sampled values or words. Mathematical calculation shows that the average time between misframes is as long as 104years and the average recovery time is less than several lines when a 4-bit reversible counter for synchronization is used in transmitting 500-kHz narrow-band TV-phone signals. View full abstract»

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  • On Economies of Scale and Integration of Services in Certain Queued Information Transmission Systems

    Publication Year: 1972 , Page(s): 991 - 995
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (488 KB)  

    This paper discusses two aspects of the performance and design of certain queued or buffered information transmission systems. Examples are buffered multiplexers and message-switching systems. The first part of the paper examines the theoretical performance of such a system as its output channel capacity and the number of its speed-limited information sources are increased proportionately. The aspects of performance considered are time delay and probability of overflow of the system's finite buffer capacity. Under the assumptions made (described in the text), system performance almost always improves as the size of the system is increased. The second portion of the paper considers the design of a communication system that must serve two classes of users, the two classes differing in average message length. Here the question is that of superiority of integrated or segregated communication system design under a channel-capacity constraint. Using average delay as a performance criterion it is shown that the integrated system is not always superior but becomes superior if there is sufficient excess capacity. View full abstract»

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  • Optimal Equalization of Discrete Signals Passed Through a Random Channel

    Publication Year: 1972 , Page(s): 884 - 890
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (688 KB)  

    The problem of equalizing a discrete signal that has been transmitted through a channel selected at random from an ensemble of channels is considered. Using mean-square error as the performance index, the minimum number of adjustable parameters required to achieve a given level of performance is sought. For certain special cases, it is shown that, using nonrecursive sampled data filters, the optimum tap weights are given by the eigenvectors of the matrix formed from the covariances of the channel's impulse response. A numerical algorithm is developed to find the optimum equalizer structure for a wide class of channels with the restriction that the number of channels in the given ensemble is finite. Results worked out for several examples show that the optimum equalizer structure requires significantly fewer adjustable parameters than the standard transversal equalizer in order to obtain the same level of performance. View full abstract»

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  • On the Performance of Digital Communication Systems with Bandpass Limiters--Part I: One-Link System

    Publication Year: 1972 , Page(s): 972 - 975
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB)  

    This paper examines the performance of a digital communication system operating in the presence of additive Gaussian noise when a bandpass hard limiter is inserted into the system. In contrast with earlier published work for large time-bandwidth product systems, small signal-time-duration-noise-bandwidth products at large SNR's are considered. It is found that the degradation introduced by the limiter is more severe under these conditions. View full abstract»

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  • The New-Word Policy for Two-Way Feedback Communication

    Publication Year: 1972 , Page(s): 1041 - 1043
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (312 KB)  

    A feedback policy, denoted the "new-word policy," is described that permits reduction in the required number of repeats compared to the method commonly proposed. An expression is derived comparing the average number of transmissions required per new word. View full abstract»

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  • Dynamic Programming Training Period for an MSE Adaptive Equalizer

    Publication Year: 1972 , Page(s): 857 - 864
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (720 KB)  

    This paper concerns itself with the design of an algorithm that will shorten the training period and adaptation time of an adaptive equalizer. Time-invariant or slowly varying channels with white additive Gaussian noise are considered. An adaptive equalizer in the form of a nonrecursive transversal filter reduces the intersymbol interference. The training period consists of the transmission of isolated pulses between which the equalizer is adjusted. The algorithm uses a minimum mean-squared error criterion with a variable step size on each iteration. A fixed number of iterations is allowed for the error to be minimized. A constraint related to the average excess mean-squared error is included, and the set of step sizes is determined by invoking the principle of optimality in dynamic programming. The resulting algorithm is compared to the popular fixed step-size algorithm. Predicted and experimental results are given. A fairly well conditioned and a poorly conditioned channel are considered. Results show that the new algorithm has a faster adaptation time. It is more complex than the fixed step-size algorithm, but for long transversal filters requires little additional computation time. View full abstract»

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  • Automatic Testing and Automatic Test Systems for Communications Systems

    Publication Year: 1972 , Page(s): 1029 - 1031
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    Over the past years, a considerable number of electronic test facilities have been converted to automatic test systems (ATE). View full abstract»

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  • Statistical Dependence Between Components of a Differentially Quantized Color Signal

    Publication Year: 1972 , Page(s): 890 - 899
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1640 KB)  

    The statistical dependence (redundancy) between three differentially coded color components of a video-telephone signal are explored by means of an entropy study. We measure the entropy of the differentially coded color baseband signals both jointly and as three separate signals. The source material consisted of a number of portraittype pictures. The color signal is treated in a format containing a baseband luminance channel and two baseband chrominance channels. Various orthogonal and nonorthogonal transformations, including the Karhunen-Loève transform, are applied to the chrominance signals to study the effect on the entropy. With a well-chosen format for the color signal, our results show that the redundancy resulting from using a separate encoding of the signals rather than a joint encoding ranges between 0.2 and 0.5 bits. The possible savings accruing from considering the relationship between coded color differential components was only about 1 percent of the total bit rate for most pictures and increased to a maximum of 4 percent for one particular picture. View full abstract»

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  • Theory of Synchronous Communications

    Publication Year: 1972 , Page(s): 1047 - 1048
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    First Page of the Article
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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.

 

 

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Robert Schober
University of British Columbia