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Communications, IEEE Transactions on

Issue 11 • Date November 1979

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  • [Front cover and table of contents]

    Publication Year: 1979 , Page(s): 0
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  • Correction to "A study of userś buffer variations in random access satellite channels"

    Publication Year: 1979 , Page(s): 1745 - 1746
    Cited by:  Papers (8)
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  • Comments on "Finite buffer behavior with poisson arrivals and random server interruptions"

    Publication Year: 1979 , Page(s): 1746
    Cited by:  Papers (2)
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  • Authors' reply

    Publication Year: 1979 , Page(s): 1746
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  • [Back cover]

    Publication Year: 1979 , Page(s): 0
    Cited by:  Papers (1)
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  • Specification and Validation of Protocols

    Publication Year: 1979 , Page(s): 1671 - 1680
    Cited by:  Papers (25)  |  Patents (1)
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    Complex protocols are used to coordinate remote activities in computer networks. To insure proper operation, formal techniques of protocol definition and validation have been proposed, and developed to the point that they can be applied to actual protocols. However, much work remains to be done in order to cope with protocols of ever-increasing complexity; in particular, those coordinating the activities of many interacting entities. The characteristics that determine the applicability of the different specification and validation techniques to a protocol will be discussed. We will define the "topology" of a protocol, and treat also protocols that are intended to work in a variety of configurations, as well as configurations which may change in time (i.e. "evolving topologies"). Finally, based on this new general point of view, a short survey of specification and validation techniques will be presented, and the extensions needed to handle complex protocol characteristics will be discussed. View full abstract»

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  • The Tradeoff Between Delay and TASI Advantage in a Packetized Speech Multiplexer

    Publication Year: 1979 , Page(s): 1716 - 1720
    Cited by:  Papers (17)  |  Patents (1)
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    A packetized speech multiplexer differs from a circuitswitched TASI system in that the presence of a packet buffer allows a tradeoff where the TASI advantage can be increased at a cost in packet delay. This tradeoff is investigated via a simulation. Results are presented to show the relations between TASI advantage and delay, for both an average delay criterion and a maximum delay criterion. It is shown that, particularly for the case where small numbers of talkers are multiplexed, the packetized system offers significant improvements in TASI advantage over the conventional circuit-switched multiplexer, at modest costs in packet delay. View full abstract»

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  • Performance of Partial Response Digital Radio Systems in Linear and Nonlinear Bandlimited Channels

    Publication Year: 1979 , Page(s): 1720 - 1725
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    Lender's partial response baseband system model is analyzed, extended and compared with two other partial response models. The feasibility of each system model in practical implementation is assessed. The effects of filter imperfections and of channel nonlinearities on the performance of QPRS digital radio systems is analyzed by means of computer simulation. View full abstract»

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  • Indicating Service Outages of High Capacity Digital Systems at the Affected Channel Banks

    Publication Year: 1979 , Page(s): 1731 - 1736
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    In a digital transmission network including 1.5 Mbit/s and higher speed systems, it is desirable to signal service outages of the higher speed systems to the multitude of affected channel banks terminating the 1.5 Mbit/s systems in order to avoid unnecessary maintenance activity. To do this, it is proposed that a special signal be transmitted to the channel banks from the multiplex terminating the higher capacity systems. This special signal causes the channel bank alarm lights to flash, and thus can be recognized without special test equipment or modification of the channel banks. While the special signal may be quite complex to operate properly with several generations of channel banks, the circuitry required to generate it fits comfortably on a single circuit board and can be shared by all 1.5 Mbit/s outputs of the multiplex. View full abstract»

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  • Error Performance of Direct Sequence Spread Spectrum Systems on Non-Selective Fading Channels

    Publication Year: 1979 , Page(s): 1696 - 1700
    Cited by:  Papers (2)
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    The effects of fading on the performance of a spread spectrum multiple-access communication system using direct sequence modulation are investigated. General series expansions are developed for the average probability of error and specific results are given for the irreducible error rate associated with propagation over independent Rician fading channels or correlated Rayleigh fading channels. Simple single-term approximations for the irreducible error rate, which are proportional to the second moment of the cross-correlation between the spreading codes employed by the users, are derived for these cases. View full abstract»

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  • 20, 30 GHz Band Cassegrain Earth Station Antenna for the Japanese Domestic Satellite Communication System

    Publication Year: 1979 , Page(s): 1728 - 1731
    Cited by:  Papers (3)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (408 KB)  

    An 11.5 m 30/20 GHz band Cassegrain antenna has been developed for a Japanese domestic satellite communication system earth station. In order to form an economical satellite communication network, the earth station antenna is required to be installed on the top of a telephone office building in a large city. Therefore, interference with terrestrial radio relay systems and antenna load on a building become the most important problems to be investigated. Considering the satellite position in geostationary orbit, a limited steerable system combined with a two-jackscrew drive mechanism is employed to lighten and simplify the antenna structure. Measured antenna aperture efficiencies are 72% in 20 GHz band and 68% in 30 GHz band. Measured wide angle radiation patterns satisfy the CCIR recommendation level. The G/T of the antenna at the feed horn port is measured to be 53.9 dB/K at El = 45\deg at 18.75 GHz. Interference with the 20 GHz band terrestrial radio relay system in extremely near field was experimentally studied. Results show that the terrestrial system's antennas can be installed closely up to about 20 m without serious interference. View full abstract»

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  • Issues in Terrestrial/Satellite Network Synchronization

    Publication Year: 1979 , Page(s): 1690 - 1695
    Cited by:  Papers (3)
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    This paper examines the key issues involved in choosing synchronization techniques applicable to both terrestrial and satellite switching networks. The terrestrial networks considered involve circuit switching, message switching, packet switching, and other integrated voice/data nodal configurations. The satellite networks considered involve time-division multiple access (TDMA) systems and their associated synchronization problems. Peculiar problems associated with satelliteswitched TDMA (SS/TDMA) network synchronization are also addressed. Finally, the issues involved in synchronizing integrated satellite/terrestrial networks are addressed. Emphasis will be placed on assessing the state of the art of current terrestial/satellite synchronization technology and projecting future trends. View full abstract»

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  • Rain Attenuation Statistics from a 19 and 28 GHz COMSTAR Beacon Propagation Experiment: One Year Cumulative Distributions and Relationships Between the Two Frequencies

    Publication Year: 1979 , Page(s): 1725 - 1728
    Cited by:  Papers (11)
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    Cumulative attenuation distributions for one year and relationships between attenuations at 19 GHz and 28 GHz are presented for an earth-space propagation path terminating at Crawford Hill, New Jersey. An example from the distributions indicates that 20 dB attenuation was exceeded for 0.012% of the year at 19.04 GHz and for 0.06% at 28.56 GHz. For both frequencies the polarization was linear and oriented 21° from vertical at the receiver. When the attenuation at 19 GHz was less than 20 dB, the attenuation in dB at 28 GHz averaged 2.1 times that at 19 GHz. This ratio was lower at higher attenuations. View full abstract»

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  • Analysis of Crosstalk Data for Maximizing PCM System Application

    Publication Year: 1979 , Page(s): 1737 - 1745
    Cited by:  Papers (2)
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    This paper addresses the general problem of estimating the maximum number of PCM systems allowed on one cable repeater section given representative PCM repeater characteristics and cable data. NEXT is analyzed, and a regenerative repeater is characterized by a graph of acceptable NEXT attenuation versus repeater section loss. Crosstalk data are utilized by statistical summation (convolution) using a flexible method based on cumulants (semi-invariants) which can deal with multiple subpopulations. An example calculation is given to illustrate the procedure for a simplified case. The relationship between the standard deviations for single frequency measurements and widebank crosstalk is discussed. View full abstract»

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  • A Generalized Adaptive Quantization System with a New Reconstruction Method for Noisy Transmission

    Publication Year: 1979 , Page(s): 1681 - 1689
    Cited by:  Papers (3)
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    To cope with the effects of channel errors, robust adaptive quantization schemes contain a leakage parameter in the step-size adaptation algorithm. Unfortunately, this mechanism also introduces its own distortion in the form of reduced dynamic range of the step size which causes the signal-to-noise ratio to drop appreciably at the far ends of the range of input signal intensities typically associated with speech applications. A method for compensating for the leakage-induced distortion is proposed here. It consists of a generalization of the adaptive quantizer with the novelty contained entirely in the decoding procedure. Whereas the reconstruction or decoded values in existing adaptive quantizers are proportional to the adapted step size, with the prespecified and fixed reconstruction parameters {\eta_{r}} giving the constants of proportionality, the generalization will have these parameters replaced by reconstruction functions {\eta_{r}(\bullet )} of the time-evolving step size. The sole time-varying parameter in the generalized quantizer is, as originally, the step size which is adapted in exactly the same manner as in existing robust quantizers. Two straightforward methods for the synthesis of the reconstruction functions are presented. The first is analytic while the second is a method for generating the functions through simulations. Computed results for two examples are presented. In the first example, the input signals are independent, Gaussian random variables. In the second example, the inputs are correlated and generated by a first-order Markov model. The communication system is adaptive differential PCM. In both examples, the generalized systems perform consistently better than existing systems and give significant improvements in SNR for signal intensities at the extremities of a 50 dB range. View full abstract»

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  • Techniques to Generate ISI and Jitter-Free Bandlimited Nyquist Signals and a Method to Analyze Jitter Effects

    Publication Year: 1979 , Page(s): 1700 - 1711
    Cited by:  Papers (13)
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    An analytical method to predict the data pattern dependent jitter is presented. Results obtained are shown to be in excellent agreement with those obtained by computer simulation and laboratory measurement. In order to find methods that can generate an ISI (intersymbol interference) and jitter-free bandlimited Nyquist signal, a double-intervaled raised cosine and its spectral characteristics are studied. Based on this, a search for new double-intervaled pulses having low spectral sidelobes is conducted. Pulses having desirable spectral characteristics and their application in communication systems are discussed. Two methods for the generation of ISI and jitter-free Nyquist signals are described. The first one uses the concept of pulse overlapping while the second one incorporates the nonlinear switching concept. These two methods are equivalent as they can generate the same output signals. Hardware implementation and measured results on this nonlinear switching filter are given. The simplicity of its design and its low cost will enable this type of nonlinear switching filter suitable for use in low bit rate satellite communication systems. View full abstract»

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  • Adaptive Schemes to Recognize an Asynchronously Generated Signal

    Publication Year: 1979 , Page(s): 1711 - 1716
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    Decision and estimation algorithms for a signal of asynchronous generation are treated with emphasis on waveform estimation. A simplified model for source statistics is assumed. Starting with a supervised learning model, two algorithms of the non-supervised type are derived. Their estimation error performance is studied by computer simulation. View full abstract»

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  • Combined Source-Channel Coding of Images

    Publication Year: 1979 , Page(s): 1644 - 1659
    Cited by:  Papers (84)
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    A combined source-channel coding approach is described for the encoding, transmission and remote reconstruction of image data. The source encoder employs two-dimensional (2-D) differential pulse code modulation (DPCM). This is a relatively efficient encoding scheme in the absence of channel errors. In the presence of channel errors, however, the performance degrades rapidly. By providing error control protection to those encoded bits which contribute most significantly to image reconstruction, it is possible to minimize this degradation without sacrificing transmission bandwidth. The result is a relatively robust design which is reasonably insensitive to channel errors and yet provides performance approaching the rate-distortion bound. Analytical results are provided for assumed 2-D autoregressive image models while simulation results are described for real-world images. View full abstract»

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  • False Lock Performance of Quadriphase Receivers

    Publication Year: 1979 , Page(s): 1660 - 1670
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (688 KB)  

    Quadriphase receivers, like biphase receivers, have the ability to false lock on a sideband of the data modulation. The theory associated with this phenomenon for receivers of binary phase-shift-keying (BPSK), using Costas loop demodulation, has recently been documented in the literature. This paper considers the corresponding theory for receivers of balanced quadriphase-shift-keying (QPSK) employing a quadriphase Costas loop (or equivalent fourth-power loop) for demodulation. Specific closed form expressions for false lock performance are developed and numerically evaluated for the particular case of single pole arm filters and an NRZ data format for each of the two statistically independent quadrature modulations. View full abstract»

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  • General Method for Calculating the Spectrum of a Zero Substitution Coded Signal

    Publication Year: 1979 , Page(s): 1637 - 1643
    Cited by:  Papers (1)
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    This paper describes a general method for calculating the power spectra of zero substitution coded signals and applies this method to calculate the B3ZS signal spectrum of the DS-3. Many digital radio systems transmit a signal which consists of DS-3 level baseband signals. Therefore, knowledge of the B3ZS spectral characteristics is important in DS-3 level interference and systems studies. The method used for calculating spectral densities of substitution coded signals is based on signal-flow graph analysis. While signal-flow graph identities and Mason's gain formula have been used in the past in the calculation of some substitution coded spectra, they become unduly cumbersome when applied towards complex spectra such as that of the B3ZS signal. In place of the graph identities and gain formula, two matrix techniques are introduced that can be used in general to simplify spectral calculations for substitution coded signals. The methodology used in analyzing these communication signals can also be applied to other related fields such as coding of signals for magnetic recordings. 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