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Communications, IEEE Transactions on

Issue 9 • Date September 1975

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Displaying Results 1 - 25 of 26
  • [Front cover and table of contents]

    Publication Year: 1975 , Page(s): 0
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    Freely Available from IEEE
  • Correction to "Low SNR Digital Communication over Certain Additive Non-Gaussian Channels"

    Publication Year: 1975 , Page(s): 1002
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  • Correction to "Image Coding via a Nearest Neighbor Image Model"

    Publication Year: 1975 , Page(s): 1007
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  • Comments on "On Linear Receivers for Digital Transmission Systems"

    Publication Year: 1975 , Page(s): 1008
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  • Correction to "Improving Automatic Repeat-Request (ARQ) Performance on Satellite Channels Under High Error Rate Conditions"

    Publication Year: 1975 , Page(s): 1008
    Cited by:  Papers (10)
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  • [Back cover]

    Publication Year: 1975 , Page(s): 0
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  • Partial-Response Signaling

    Publication Year: 1975 , Page(s): 921 - 934
    Cited by:  Papers (250)  |  Patents (64)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1424 KB)  

    This paper presents a unified study of partial-response signaling (PRS) systems and extends previous work on the comparison of PRS schemes. A PRS system model is introduced which enables the investigation of PRS schemes from the viewpoint of spectral properties such as bandwidth, nulls, and continuity of derivatives. Several desirable properties of PRS systems and their relation to system functions are indicated and a number of useful schemes, some of them not previously analyzed, are presented. These systems are then compared using as figures of merit speed tolerance, minimum eye width, and signal-to-noise ratio (SNR) degradation over ideal binary transmission. A new definition of speed tolerance, which takes into account multilevel outputs and the effect of sampling time, is introduced and used in the calculation of speedtolerance figures. It is shown that eye width, a performance measure that has not been used previously in comparing PRS systems, can be calculated analytically in many cases. Exact values as well as bounds on the SNR degradation for the systems under consideration are presented. The effect of precoding on system performance is also analyzed. View full abstract»

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  • The Performance of a Digital FM System with Discriminator: Intersymbol Interference Effects

    Publication Year: 1975 , Page(s): 867 - 878
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (952 KB)  

    The error performance of a digital FM system is studied in the presence of additive Gaussian noise. This system is a conventional one employing a voltage-controlled oscillator as the modulator and a limiter-discriminator followed by a low-pass filter as the demodulator. The notion of "clicks" introduced by Rice, and used by Mazo and Salz, is adopted and the performance of the above system is theoretically studied when the intersymbol interference caused by band limitation cannot be neglected. Special consideration has been given to binary frequency-shift keying (FSK) systems. For such systems, the probability of error is given in a closed form. View full abstract»

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  • The Residual Encoder--An Improved ADPCM System for Speech Digitization

    Publication Year: 1975 , Page(s): 935 - 941
    Cited by:  Papers (35)  |  Patents (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (752 KB)  

    An improved system for speech digitization using adaptive differential pulse-code modulation (ADPCM) is described. The system uses an adaptive predictor, an adaptive quantizer, and a variable length source coding scheme to achieve a 4-5 dB increase in signal-to-noise ratio over previous ADPCM. The increase can be used to improve speech quality at moderate data rates on the order of 16 kbits/s or to retain the same quality and reduce the data rate to 9.6 kbits/s. The latter alternative permits the use of narrow-band channels. The implementation complexity is on the same order as other ADPCM systems. View full abstract»

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  • A New Technique for Recording High-Voltage Transients in Telephone Networks

    Publication Year: 1975 , Page(s): 962 - 970
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    Some basic difficulties in the protection of telephone networks against dangerous overvoltage disturbances such as lightning are discussed, and a new method for measuring and recording such transients is presented. The method essentially consists of measuring the analog disturbance signals, converting and coding their temporal values into digital numbers easily available to shift register memories and subsequently recording the results either with a teleprinter for computer analysis and statistical abstracts or with a xy -recorder for a human observer. The instrument is capable of recording disturbance amplitudes of 0.1-MHz spectral content linearly with an 300-V interval up to voltages of 5 kV, the sampling rate of the A/D converter used for the recording being adjustable to values of 500 kHz, 1 MHz or 2 MHz. The digital circuits of the instrument use positive logic and are realized for the most part by TTL and MOS technologies. View full abstract»

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  • A Technique of PCM Transmission over 2 GHz Microwave Radio

    Publication Year: 1975 , Page(s): 1004 - 1007
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    The application of multiplexed PCM channels to a microwave radio system is attractive in areas where geographic terrain limits the practicality of cable plant construction. A technique of interfacing the digital signal with an analog radio baseband is described. The successful Inclusion of a voice-frequency (VF) orderwire at the low frequency end of the digital spectrum without a significant penalty in error-rate performance demonstrates the efficiency of the technique. View full abstract»

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  • Nonlinear Distortion Analysis in the Frequency Demodulator Using Feedback

    Publication Year: 1975 , Page(s): 884 - 891
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (688 KB)  

    A general method for the accurate analysis of the response of a frequency demodulator using feedback (FMFB) to an arbitrary frequency modulated (FM) signal is developed. This approach is employed to determine the FMFB outputs for two specific modulating signals, Gaussian noise, and a single sine wave. The proposed method is then applied to three different FMFB configurations differing in their low-pass filter structure. As a result, generalized curves enabling easy evaluation of the intermodulation (IM) distortion and the harmonic distortion are obtained. When designing the FMFB on the basis of these results, the influence of the relevant system parameters, such as IF filter bandwidth, feedback factor, position of the channel in the baseband, structure of the low-pass filter, etc., on the nonlinear properties of the FMFB can be controlled, simply and in a straightforward manner. The accuracy of the method has been verified in those rare cases for which solutions are already known. View full abstract»

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  • On ML Bit Detection of Binary Signals with Intersymbol Interference in Gaussian Noise

    Publication Year: 1975 , Page(s): 971 - 976
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (600 KB)  

    Various forms and properties of the maximum-likelihood (ML) bit detector structure for binary signals with intersymbol interference in the presence of additive stationary Gaussian noise are presented and two receiver implementation forms are considered. A simple analytical approximation which also has a heuristic interpretation as a lower bound on the bit probability of error for this detector is presented. The performance of this detector for typical small and moderate degrees of intersymbol interference is presented and compared to other detectors. Both cases indicate that the analytical approximation is quite tight and thus useful in predicting the performance of this highly nonlinear device. View full abstract»

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  • Receiver Design for Multilevel Digital Optical Fiber Systems

    Publication Year: 1975 , Page(s): 987 - 994
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (704 KB)  

    We consider the design of a receiver for a digital optical fiber system operating with multilevel pulse amplitude modulation. This form of modulation provides for high bit rates on digital systems employing large diameter optical fibers and LED sources. The receiver configuration analysis is one with a p-i-n avalanche photodetector and a FET preamplifier. The analysis is complicated by the fact that the signal levels and threshold boundries have to be nonuniformly spaced to cope with signal dependent shot noise introduced by the photodiode detector. An algorithm for level placement is reported. Performance figures for typical systems, with optical pulse shape which are either Gaussian or exponential, are calculated. View full abstract»

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  • An Implanted Telemetry Unit for Ambulatory Animals

    Publication Year: 1975 , Page(s): 983 - 987
    Cited by:  Papers (2)
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    An implanted physiological-signal telemetry unit for an ambulatory animal is described. It uses a single 1.35 V mercury cell, is 1 \times 2.5 \times 4 cm in size, and weighs 15 g. Transcutaneous RF turn-on and magnetic turn-off are used to conserve battery power. The battery can operate 175 h before replacement. An integrated circuit amplifier supplies a voltage gain of 250 over a nominal band from 0.2 Hz to over 4 kHz. With 2 mV peak input, it yields 75 kHz peak deviation of a 20 MHz carrier. Relations between frequency, Q , receiving antenna voltage, and implant coil diameter are derived. Circuits are also given for a "turn-on" device, a 20 MHz converter, and the sequential gating of three mutually perpendicular antennas to avoid dropouts as the animal moves within the cage. View full abstract»

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  • Analysis and Digital Realization of a Pseudorandom Gaussian and Impulsive Noise Source

    Publication Year: 1975 , Page(s): 849 - 858
    Cited by:  Papers (6)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1008 KB)  

    This paper presents results on the analysis and digital hardware realization of a non-Gaussian impulse noise source which can be used to model the impulsive noise present in wide-band communications systems. The impulse noise appearing in practical systems is characterized by bursts of much higher amplitudes than would be predicted by a normal- or Gaussian-distribution law. A need exists for a better characterization of this non-Gaussian impulsive noise as well as actual noise generators which can be used for evaluation of present and future communications equipment under realistic system-operating conditions. The impulse noise model and the realization of the noise generator described in this paper are capable of producing Gaussian background noise, lognormal impulsive noise, and burst timing to set prescribed starting and ending times of the bursts and impulse density within each of the burst periods. The techniques used in this paper are based on first generating a basic pseudorandom binary sequence (PRBS) and then from this deriving the Gaussian background noise by adding samples from the PRBS generator. The lognormal noise is then derived from the same sequence by using an incremental exponential generator. The burst timing signals which realize an approximate Poisson distribution are obtained by observing the occurrences of specific subsequences from the PRBS generator. View full abstract»

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  • Video Encoding Using an Adaptive Digital Delta Modulator with Overshoot Suppression

    Publication Year: 1975 , Page(s): 905 - 920
    Cited by:  Papers (3)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1448 KB)  

    An overshoot suppression scheme to improve the performance of the digital Song adaptive delta modulator (DM) for picture transmission is described. This scheme allows for a faster increase in the step sizes than permitted by overshoot and settling time considerations, thus improving rise-time performance. The overshoot suppression (OSS) algorithm used has been verified using computer simulation on a PDP-8. Furthermore, experimental results using computer generated test pictures as well as pictures from a flying-spot scanner show the improvements due to the overshoot suppression scheme. It is also shown that the additional hardware required for the actual implementation of the algorithm is simpler than those encountered in the literature, and gives better signal-tracking accuracy. Upper bounds for the settling time, with and without OSS, are derived showing an improvement with the suppression scheme. Stability conditions are also derived permitting the proper selection of DM parameters. View full abstract»

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  • Solution to a Class of Optimization Problems with Amplitude Constraints

    Publication Year: 1975 , Page(s): 979 - 983
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (384 KB)  

    Let H[s(\bullet ),t] be a functional of the function s(\bullet ) and the independent variable t . The criterion functional J(s) is defined to be the integral of H over T , a set of points t . The problem considered is the maximization of J(s) with respect to an amplitudeconstrained function s . Necessary conditons for the optimal solution are obtained, and a method of determining the optimum s is given. Some examples are presented to clarify the theorems and their applications. View full abstract»

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  • Packet Switching in a Multiaccess Broadcast Channel: Dynamic Control Procedures

    Publication Year: 1975 , Page(s): 891 - 904
    Cited by:  Papers (106)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1392 KB)  

    In a companion paper [1], the rationale for multiaccess broadcast packet communication using satellite and ground radio channels has been discussed. Analytic tools for the performance evaluation and design of uncontrolled slotted ALOHA systems have been presented. In this paper, a Markovian decision model is formulated for the dynamic control of unstable slotted ALOHA systems and optimum decision rules are found. Numerical results on the performance of controlled channels are shown for three specific dynamic channel control procedures. Several practical control schemes are also proposed and their performance compared through simulation. These dynamic control procedures have been found to be not only capable of preventing channel saturation for unstable channels but also capable of achieving a throughput-delay channel performance close to the theoretical optimum. View full abstract»

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  • Bandwidth Reduction of Video Signals via Shift Vector Transmission

    Publication Year: 1975 , Page(s): 1002 - 1004
    Cited by:  Papers (9)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (336 KB)  

    An experimental shifting technique applied to real television images in order to reduce their redundancy is described. The technique consists of dividing the images into zones and then transmitting vectors that connect correlated zones in successive frames. A threshold which is a function of frame-to-frame zone velocity and inherent points luminance is introduced to determine the shift vector. Image reconstructions are obtained with an information rate equal to 0.7 bit/pel. View full abstract»

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  • Surprising Properties of Two-Level "Bandwidth Compaction" Codes

    Publication Year: 1975 , Page(s): 878 - 883
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (680 KB)  

    This paper investigates some of the properties of a class of two-level codes with constrained run length, whose use has been proposed for purposes of bandwidth compression. It is shown that such codes can indeed reduce the bandwidth containing a given percentage of the transmitted power. To communicate information, however, different transmitted codewords must be distinguishable at the receiver, and this requires that the channel bandwidth be sufficiently wide to allow the difference waveform to propagate. It is demonstrated that decreasing the X -percent bandwidth using these codes leads to a rapid increase in the difference waveform bandwidth, and hence in the channel bandwidth necessary to maintain error rate performance. Thus, these codes are bandwidth expansion codes in disguise. Signal-to-noise ratio and channel bandwidth requirements for these codes are discussed and compared with those of M -level codes [pulse-amplitude modulation (PAM)] for two kinds of receivers. View full abstract»

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  • Carrier and Clock Recovery from Transversal Equalizer Tap Settings for a Partial Response System

    Publication Year: 1975 , Page(s): 976 - 979
    Cited by:  Papers (2)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (344 KB)  

    A general expression is derived for the tap settings of a linear transversal equalizer using the minimum mean-square error (MMSE) criterion when the class-4 partial-response (PR) signal is distorted by noise as well as carrier phase and timing errors. The values of the tap settings are used to reduce the carrier and timing phase errors. View full abstract»

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  • Polarization Tracking of a Partially Coherent Signal Using a Double Loop

    Publication Year: 1975 , Page(s): 859 - 866
    Cited by:  Papers (2)
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    We consider the problem of simultaneously estimating the phase and polarization angles of a linearly polarized electromagnetic wave. The solution of this problem has applications to space communications and ionospheric probing. The nonlinear stochastic characteristics of a cross-coupled double-loop implementation for the tracker are evaluated using the multidimensional Fokker-Planck equation. The exact stationary probability density is found for a special case of equal signal-to-noise ratio (SNR) in the two loops. The stationary probability density is obtained for a general class of double loops when the two loop bandwidths differ greatly. View full abstract»

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  • Simulation of Centralized Computer Communications Systems

    Publication Year: 1975 , Page(s): 994 - 1001
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (776 KB)  

    In this concise paper we described the simulation approach for a general centralized computer communication system with emphasis on efficiency and versatility. The simulation program consists of three modules representing different levels in a hierarchy. The lowest level models the polled multidrop line connecting remote terminals to the concentrator. The second level models the trunk lines and the concentrator which interfaces the multidrop lines of lower speed to one or more higher speed trunk lines connected to a central computer. The highest level models the central computer which communicates with remote terminals via the trunks. A hybrid simulation approach is used to ease program development and to shorten computer running time. When feasible, empirical distributions, analytical formulas, or analytical models are used to eliminate simulation steps and simplify simulation procedures. The techniques developed are illustrated by application to the NASDAQ system. View full abstract»

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  • Behavior of Crosstalk Loss for Adjacent Pairs at Low Frequencies

    Publication Year: 1975 , Page(s): 956 - 962
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (480 KB)  

    Measurements at the Northern Electric cable plant in Lachine [2] and elsewhere [3],[4] showed that at low frequencies near-end crosstalk loss (NEXT) and far-end crosstalk loss (FEXT) for adjacent pairs do not have slopes of 15 dB/decade and 20 dB/ decade, respectively. In this paper an approximation predicts a slope of 5 dB/decade for NEXT and long cable and 10 dB/decade for FEXT. 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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Meet Our Editors

Editor-in-Chief
Robert Schober
University of British Columbia