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Communication Technology, IEEE Transactions on

Issue 3 • Date June 1968

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Displaying Results 1 - 25 of 31
  • [Front cover and table of contents]

    Page(s): 0
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    Freely Available from IEEE
  • Asynchronous time multiplexing

    Page(s): 349 - 357
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    The use of asynchronous adaptive sampling for multiplexing multichannel analog signals and data over a synchronous digital facility is examined. This method promises to provide an efficient and consistent way to digitally transmit voice, line-scanned graphics or text, and data. Buffer analysis, computer simulations, and laboratory prototypes are described. When multiplexing speech using extremal sampling, quality of about 32 000-bit companded pulse-code modulation (PCM) is achieved at an average bit rate of 13 000 bit/s per user. Idle spaces, up to 20 percent of the link capacity, can also be filled with indirect data. The potential demonstrated in the laboratory indicates that effort should be directed toward reducing system complexities so as to achieve an efficient, practical system. View full abstract»

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  • Traffic Considerations with TONE-DIAL® Telephones

    Page(s): 357 - 364
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    This paper compared two methods of operation of receivers for pushbutton calling using voice frequency signaling. It compares the traditional system in which the tone receiver is connected for the full dialing interval with a system in which the receiver is connected only during the instant of tone generation when a pushbutton is operated. Not surprisingly, the results indicate that a smaller number of receivers is required in the latter case. Representations are made that the more complex station and central office detection equipment required in the latter case is less expensive than the additional receivers needed for the former with an acceptable grade of service. View full abstract»

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  • Dictionary of English Language Traffic Terms

    Page(s): 365 - 369
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    A list of English language terms related to the handling of traffic, which are in use by manufacturers and users of communication systems, is provided. The list was prepared by the Nomenclature Committee of the International Teletraffic Congress and represents current usage rather than an adopted standard. View full abstract»

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  • Signaling of Remotely Controlled Railway Trains

    Page(s): 369 - 374
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    A train control system has been evaluated in which a remote digital computer is used as the feedback element of a servomechanism. Telemetry signals are required between the train and computer and in the reverse direction, and engineering constraints are placed on the implementation. Signaling requirements are described, and experimental measurements of the electrical noise and ensuing analyses are presented. Equipment using phase and frequency modulation was built and tested, and a serial coding system was tested at typical railway properties. Measurements were made at diminishing power levels in order to determine margins of communication security; error rates approaching 1 in 105are anticipated for an operating train control system. View full abstract»

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  • Data Transmission Through a Random Noisy Channel by PAM

    Page(s): 375 - 379
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    A criterion of minimum mean square error is used to specify the optimum, linear, time-invariant equalizer for a system in which data are transmitted by pulse amplitude modulation through a randomly selected channel. The results are applied to the case in which the received pulse is a synchronous demodulation of a passband pulse, with the phase of the demodulating oscillator a random variable and with a random time delay. The results can be applied to automatic equalization. During adjustment intervals, an automatic equalizer can use its channel measurement to specify a set of possible channel measurements instead of using it as a single exact measurement. The parameters of the automatic equalizer are then set in such a way that performance will be satisfactory over the "smeared" measurement set, reducing the sensitivity of the equalizer's performance to measurement error. View full abstract»

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  • Performance Monitor Techniques for Digital Receivers Based on Extrapolation of Error Rate

    Page(s): 380 - 387
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    There is a need in many digital communication systems to estimate the current digital error rate of the receiver without the use of special transmissions and without interrupting traffic flow. Devices for performing this function have been termed performance monitor units (PMU). As an element of an adaptive communication system, the PMU could be used to determine when adaptive change is needed and, by comparing the error rates which would result from the various available choices of adaptation, to select the best change to be made at any time. This paper describes a PMU technique which is applicable to a wide class of digital modulation methods. Details are given for the cases of noncoherent frequency shift keying (FSK), differentially coherent phase shift keying (PSK), and coherent PSK receivers operating over a fading channel. View full abstract»

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  • A Performance Monitoring Scheme for FSK Transmission over Fading Channels

    Page(s): 388 - 392
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    A scheme for monitoring performance of a frequency-shift-keyed (FSK) transmission over a selectively fading channel with a nonfading component is treated. The design of the monitoring scheme is based heavily on the assumption that the received signal and additive noise are Gaussian. The monitoring requires no special test signal. An asymptotically unbiased estimate of error probability is obtained in terms of four measurements of the received signal. The measurement time required for a reliable estimate of error probability is determined. View full abstract»

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  • Maximum-Likelihood Receiver for Digital Data Transmission

    Page(s): 392 - 398
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    The maximum-likelihood (ML) receiver for binary data, additive Gaussian noise, and nearest-neighbor intersymbol interference (ISI) is shown to be a matched filter followed by a feedback loop and a tapped delay line. The loop and the tap connections contain nonlinear amplifiers, each saturating at the level of the ISI. This receiver minimizes the persymbol probability of error Pe; upper and lower bounds on Peare obtained. The mathematical receiver specifications for multilevel data and for extensive ISI are given; an approximate structure for the latter receiver is presented as an intuitive extension of the binary, limited ISI structure. View full abstract»

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  • Cascade Decoding of Cyclic Product Codes

    Page(s): 398 - 402
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    In this paper, it is shown how to synthesize simple decoders for cyclic product codes. Cyclic product codes may be synthesized in the form of interlaced codes if the block lengths of the codes are relatively prime. In this case, the decoder can be synthesized in the form of a cascade of decoders, each of which operates on one of the subcodes forming the product code. The cascade decoders described differ from most of the decoders given in the coding literature in two major respects. First, they can be built. Second, instead of correcting all error patterns with weight less than some fixed value and no error patterns of greater weight, cascade decoders correct many error patterns beyond their guaranteed correction capability. Thus, the effective error-correction performance using a cascade decoder may be considerably beyond the usual Elias bound for product codes. View full abstract»

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  • Suboptimum Rank Detection Procedures Using Rank Vector Codes

    Page(s): 402 - 410
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    A nonparametric detection scheme using only the relative ordering information of a set of samples is applied to the problem of signal discrimination. A class of codes called rank vector codes is presented and their application in this suboptimum discrimination scheme is discussed. View full abstract»

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  • Error Performance of Differential Phase-Shift Transmission over a Telephone Line

    Page(s): 411 - 419
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    This paper considers differential phase-shift transmission over a bandlimited channel with specified phase and amplitude characteristics. The problem treated is the prediction of feasible data rates and corresponding error rates over such channels. An expression is given for the probability of error. This expression takes into account intersymbol and interchannel interference when differential phase-shift keying (DPSK) modulation is used. A distortion index which is a measure of phase error is defined, and the concept of phase opening is used which parallels the concept of eye opening commonly employed in the amplitude-shift keying (ASK) modulation. The analytical methods are applied to illustrate the effects of various parameters on the performance of a high data rate transmission system over a telephone line. Results indicate that for a carefully equalized line, a single-tone system should be used, and that higher order phase alphabets are to be preferred as the bit rate increases. View full abstract»

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  • Phase Measurement Accuracy with Modulated Sounding Signals

    Page(s): 419 - 429
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    In this paper the problem of measuring an unknown carrier phase shift of a transmitted sounding signal in a Gaussian noise channel is considered. Receivers which minimize the probability that phase error is larger than some value are considered. In some cases, this criterion leads to simple phase measurement techniques. When it does not, suboptimum receivers are considered. The main objective is to determine the effectiveness of the various measurement techniques by finding the cumulative probability distribution of phase error. In this way, three sounding signals are compared: an unmodulated carrier, a binary phase shift keyed (PSK) carrier, and a Gaussian pulse amplitude modulated carrier. View full abstract»

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  • A Performance Monitoring Technique for Arbitrary Noise Statistics

    Page(s): 430 - 435
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    A technique for monitoring performance of a pilottone phase-shift-keyed system over fading channels is treated. An important feature of this technique is that it requires no prior knowledge of the statistics of the additive noise or interference. The error probability is estimated without interrupting the data transmission or sending a special test signal. The measurement time required for a reliable estimate of error probability is determined for both Gaussian and lognormal additive noise. It is shown that the necessary measurement time depends strongly on the statistics of the noise, the order of diversity, and the actual error probability. View full abstract»

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  • A Pseudorandom Multiplex System for Facsimile Transmission

    Page(s): 436 - 438
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    In this paper, a novel facsimile transmission system is proposed in which several pseudorandomly scanned pictures are superimposed on one another and transmitted through a common channel. The noise in the received pictures due to cross-interference and channel disturbances is discussed, and some results from computer simulation are presented. View full abstract»

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  • Communications Via Seismic Waves Employing 80-Hz Resonant Seismic Transducers

    Page(s): 439 - 444
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    The design, construction, deployment, and operating characteristics of experimental 80-Hz resonant seismic transmitterand receiver-transducers are discussed. A description is given of seismic-acoustic measurements and experiments involving 80-Hz signal transmissions 1) between surface sites in flat terrains, 2) between surface sites in mountainous terrains, 3) between locations on lake ice, and 4) from a surface site to locations underground inside a deep mine via earth, ice, and water media. Results of these experiments are evaluated with regard to the realization of "hard line" communications capabilities by seismic-acoustic and electrical means. View full abstract»

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  • A Ray-Tracing Analysis of a Prolonged Fadeout on an Obstacle-Diffraction Radio Path

    Page(s): 445 - 450
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    A prolonged fadeout on a long obstacle-diffraction radio path was probably caused by persistent super-refractive conditions in the lower atmosphere. Ray tracings based upon the observed refractivity profiles at nearby radiosonde stations indicated that during the outage period the beam intersected several high ridges in front of the diffracting obstacle, greatly increasing transmission loss on the circuit. Angle diversity may produce some operational improvement. View full abstract»

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  • Combiner Performance Using Narrow-Band Noise Filtering and Enhanced Squelch

    Page(s): 451 - 455
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    The use of "narrow-band" noise filters in the combiner control circuits of a quadruple-diversity post-detection combiner was found to reduce the average bit-error rate by a factor of 4.6; while the median output signal-to-noise ratio was increased by 2 dB. The use of an "enhanced-squelch" control of the postdetection combiner increased the output voice-channel signal-to-noise ratio by 3 dB, and effectively eliminated a high percentage of the noise bursts in the voice channels. View full abstract»

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  • Compact High-Powered Frequency Multipliers for S-Band Telemetry Frequencies

    Page(s): 456 - 459
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    This paper describes reliable solid-state stripline frequency multipliers that develop an output power in excess of 16 watts atSband. An overall efficiency of 46 percent is achieved for two cascaded doublers that have adequate varactor diode temperature derating to permit continuous operation at 90°C heat sink temperature. The stripline construction techniques use solid dielectric with 1/8-inch ground plane spacing permitting an extremely rugged compact package. The wide dynamic bandwidth of these devices permits the design of high linearity, wide-band, solid-state telemetry links. A technique is described that permits parallel operation of varactor diodes with inherently high isolation that ensures equal power sharing. The general design steps are also discussed. Data are presented that illustrate input-output power linearity, temperature stability, spurious signals, and bandwidth. View full abstract»

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  • The Monolithic FM Discriminator A New Piezoelectric Device

    Page(s): 460 - 463
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    The concept of controlled acoustic coupling between thickness shear trapped energy resonators fabricated on a single quartz plate led to the development of the monolithic crystal filter. Recent work at the Bell Telephone Laboratories has resulted in the development of a three-port monolithic structure capable of providing the frequency-selective network required for an FM discriminator. This device is capable of providing good linearity over bandwidths ranging from about 0.005 percent to nearly 0.2 percent at center frequencies in the range from 5 MHz to 40 MHz. An analysis of the equivalent network is given, as well as the design procedure. Experimental results from a model having a 15MHz center frequency and 6-kHz linear bandwidth are discussed. View full abstract»

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  • The Mathematical Equivalence of Digital Troposcatter Models

    Page(s): 464 - 467
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    In the past, various mathematical models have been developed for the digital troposcatter channel. Each model is amenable to the analysis of some types of systems but leads to mathematical difficulties in the analysis of others. When various transmission techniques are to be compared, a set of analyses which uses a different channel model for each system is not satisfactory unless it can be shown that the models are mathematically equivalent. In this paper, it is shown that two of the currently accepted models, the Kailath tapped delay line model and the Sunde model, are equivalent and thus yield results which may be legitimately compared. In addition, procedures are derived for mapping the parameters for each model into their equivalent parameters for the other. View full abstract»

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  • Monitoring, Telemetry, and Control for Rapid Transit

    Page(s): 467 - 475
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    The San Francisco Bay Area Rapid Transit District is building a new rapid transit system on which trains will operate automatically. Multipurpose channels and terminals will be used to monitor and control train operation, electrification, and support facilities. Incoming data and events are to be transmitted and processed digitally. System supervisory control signals, whether incoming or outgoing, will be transmitted in a binary coded form. Displays, control consoles, and voice communication sets are located in one central office where all system adjustments and decisions will normally originate. A computer in this office will operate all normal functions, initiate certain off-normal functions, perform auxiliary data and event recording, and run simulations as required. Requirements for security, reliability, flexibility, and speed are essentially alike for the different functions. This will enable use of a group of communication channels having uniform characteristics and terminations. Thus, functions may be reassigned to any channel without sacrifice of quality or security. Essential performance goals of the digital transmission system channels and terminals are specified. In addition, the specification requires tests of prototype terminals operating through noisy channels. The control computer will be used to monitor security, reliability, and margins of channels and terminal equipment, and to initiate or suggest channel reassignments. Capability of the computer programs to check data transmission effectiveness and to detect or correct errors may be expanded by further programming if experience should indicate a need. View full abstract»

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  • On Optimizing Subsystem Administrative Intrafaces in Telemetering and Supervisory Control Systems

    Page(s): 475 - 478
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    Complex telemetering, control, and supervisory systems ordinarily comprise a multitude of subsystems. Frequently, the entire system is controlled and/or maintained by two or more administrative entities. Thus, the interfaces between the various subsystems may involve administrative as well as electrical and mechanical considerations. It is evident that optimum functioning of the system requires that all subsystems must be compatible with and even complement one another. It is proposed that the key concept involved is that the administrative interfaces should be located at electrical or mechanical interfaces that can be defined by the least number of easily measured noncritical parameters. View full abstract»

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  • PCM Data Reliability Monitoring Through Estimation of Signal-to-Noise Ratio

    Page(s): 479 - 486
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    Reliability monitoring of digital pulse-code modulation (PCM) data in coherent transmission systems can be based upon online estimation of signal-to-noise ratio (SNR) at the receiver. Maximum likelihood SNR estimation is analyzed to determine the structure of the estimator and its ability to monitor error rates with a given degree of confidence. In particular, relationships between estimation confidence intervals, observation time, word error rates, and PCM word structure are developed. View full abstract»

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  • Spectral Analysis of a PAM-FM Signal

    Page(s): 487 - 491
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    A PAM-FM telemetry system has been analyzed when the various sensors or telemetering transducers each monitor a stationary Gaussian random process (GRP). Each GRP sensor output is band limited and instantaneously sampled at the optimum rate. This optimum frequency is the minimum sampling rate that causes no signal distortion due to aliasing in the frequency domain. A maximum number of sensors are accommodated with timedivision multiplexing so that the composite PAM multiplexed signal is also assumed to be a Gaussian random process. This PAM multiplexed signal is then considered to be the input modulating signal to an FM transmission system. A FORTRAN computer program has been used to obtain the resulting PAM-FM output spectral distributions for various mean square values of the PAM multiplexed signal. View full abstract»

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Aims & Scope

This Transactions ceased publication in 1971. The current retitled publication is  IEEE Transactions on Communications.

Full Aims & Scope