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Communications, IEEE Transactions on

Issue 6 • Date June 1983

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  • [Front cover and table of contents]

    Publication Year: 1983 , Page(s): 0
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    Freely Available from IEEE
  • Comments on Electronic Techniques for Pictorial Image Reproduction

    Publication Year: 1983 , Page(s): 846 - 848
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (624 KB)  

    The role of dither threshold matrices has not been paid much attention in a recent paper [1]: These comments highlight the useful features of the so-called Nasik pattern as a threshold matrix. It is shown that the total number of Nasik type matrices is 384. The properties of Nasik patterns are invariant to dyadic shifts. Hence, random selection of matrices and adaptive selection schemes can be devised, resulting in a minimization of texture and good rendition of details. View full abstract»

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  • [Back cover]

    Publication Year: 1983 , Page(s): 0
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    Freely Available from IEEE
  • Anomalous Union Bound Behavior for MFSK Signaling on Inverse Linear Channels

    Publication Year: 1983 , Page(s): 848 - 849
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (200 KB)  

    Application of the union bound to MFSK signaling on certain channels where probability of bit error varies in an inverse linear fashion with E_{b}/N_{0} can lead to the erroneous conclusion that performance degrades with increasing alphabet size. The anomaly is shown for the worst-case partial band Gaussian interference channel and the Rayleigh fading channel. View full abstract»

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  • A Performance Study of NLA 64-State QAM

    Publication Year: 1983 , Page(s): 821 - 826
    Cited by:  Papers (6)  |  Patents (52)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (560 KB)  

    The performance of a modulation technique which is both power and bandwidth efficient, termed nonlinearly amplified 64-state quadrature amplitude modulation (NLA 64-state QAM), is studied. To assess the effects of selective fading and/or system filter imperfections, computer simulated results are presented which show the sensitivity of the modulation technique to typical group delay and amplitude distortions. In addition to the above-mentioned results, the effects of modulator imperfections in the power level combining on the Peperformance are evaluated. View full abstract»

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  • A Distributed Algorithm for Minimum Weight Directed Spanning Trees

    Publication Year: 1983 , Page(s): 756 - 762
    Cited by:  Papers (23)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (712 KB)  

    A distributed algorithm is presented for constructing minimum weight directed spanning trees (arborescences), each with a distinct root node, in a strongly connected directed graph. A processor exists at each node. Given the weights and origins of the edges incoming to their nodes, the processors follow the algorithm and exchange messages with their neighbors until all arborescences are constructed. The amount of information exchanged and the time to completion are O(|N|^{2}) . View full abstract»

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  • Performance of an FH Multilevel FSK for Mobile Radio in an Interference Environment

    Publication Year: 1983 , Page(s): 840 - 846
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (600 KB)  

    This paper considers a frequency-hopped multilevel frequency shift keying (FH-MFSK) spread-spectrum communication system applied to cellular mobile radiotelephony. We present a mobile-to-base transmission model that allows us to study system impairments, such as interference from nonsynchronous users and adjacent frequency channels in the presence of matched tuned receiver filters. For interceli interference, the usual Gaussian approximation is used, but the variance calculation takes into account shadow fading. Power control in the mobiles, a mean path loss exponent of -3.5 and fast Rayleigh and slow Iognormal fading have been assumed. We have obtained results with mobile-to-base communication of 32 kbits/s per user in a 20 MHz (one-way) bandwidth. In an isolated cell system a bit error probability less than 10-3can be maintained with up to 110 simultaneous users for practical average SNR ratio of 25 dB. The presence of intercell interference degrades the bit error probability enormously, and clustering of cells is required for controlling interference. View full abstract»

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  • Unauthorized Descrambling of a Random Line Inversion Scrambled TV Signal

    Publication Year: 1983 , Page(s): 816 - 821
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    Simple techniques for unauthorized descrambling of a random line inversion scrambled television signal are proposed. An analysis of the complexity of the proposed descrambling process is presented and it is shown that high-quality estimates of moderately long encoding sequences can be obtained with reasonable memory and delay. An improvement to the basic scheme which substantially reduces memory requirements with only a slight increase in delay is also evaluated. Finally, it is shown that varying code lengths among a finite number of alternatives does not significantly increase descrambler complexity. View full abstract»

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  • The Uses of Kosten's Systems in the Provisioning of Alternate Trunk Groups Carrying Heterogeneous Traffic

    Publication Year: 1983 , Page(s): 741 - 749
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (696 KB)  

    A functional recursive scheme is described and linked with the equivalent random theory to estimate heterogeneous call blocking probabilities and "overflow" variances in toll network trunk groups. It is then used to calculate exactly the call blocking probabilities in multidimensional Kosten overflow and Engset finite source models. Numerical examples are shown. View full abstract»

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  • Implementation of a Multirate Speech Digitizer

    Publication Year: 1983 , Page(s): 775 - 783
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (928 KB)  

    In this paper, implementation of a compact and efficient multirate speech digitizer with variable transmission rates of 2.4, 4.8, 9.6, and 14.96 kbits/s is presented. The multirate algorithm has been made based on the residual-excited linear prediction (RELP) vocoder with a transmission rate of 9.6 kbits/s. The residual encoder employed in the RELP vocoder uses hybrid companding delta modulation (HCDM). This HCDM is also used as a 14.96 kbit/s coder. If the residual in the RELP system is down-sampled before encoding, a 4.8 kbit/s coder can be realized. If the residual encoder is not used, a 2.4 kbit/s linear predictive coder (LPC) can be realized by incorporating a pitch extractor. In the 4.8 and 9.6 kbit/s coders the pitch-implanted residual excitation method has been used to generate the excitation signal to the synthesis filter. The multirate speech digitizer algorithm has been implemented using 2900 series bit-slice microprocessors. The external memory is composed of 2K RAM's and 2K ROM's. The system design is a two-bus structure with a 204 ns cycle time. With efficient hardware and software design, the multirate speech digitizer requires almost the same hardware complexity as compared with the conventional 2.4 kblt/s LPC vocoder. View full abstract»

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  • An Approximate Formula for Individual Call Losses in Overflow Systems

    Publication Year: 1983 , Page(s): 808 - 811
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB)  

    A simple approximate formula for estimating individual call losses in overflow systems is derived using the interrupted Poisson process. The formula presents good accuracy in the single-overflow model, and it is also applicable to the multioverflow model. It is expected that the present formula is useful for the optimization of systems under given service criteria. View full abstract»

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  • Multiprocessor Implementation of Adaptive Digital Filters

    Publication Year: 1983 , Page(s): 826 - 835
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (920 KB)  

    Adaptive filters, employing the transversal filter structure and the least mean square (LMS) adaptation algorithm, or its variations, have found wide application in data transmission equalization, echo cancellation, prediction, spectral estimation, on-line system identification, and antenna arrays. Recently, in response to requirements of fast start-up, or fast tracking of temporal variations, fast recursive least squares (FRLS) adaptation algorithms for both transversal and lattice filter structures have been proposed. These algorithms offer faster convergence than is possible with the LMS/ transversal adaptive filters, at the price of a five-to-tenfold increase in the number of multiplications, divisions, and additions. Here we discuss architectures and implementations of the LMS/transversal, fast-converging FRLS filter, and lattice filter algorithms which minimize the required hardware speed. We show how each of these algorithms can be partitioned so as to be realizable with an architecture based on multiple parallel processors. View full abstract»

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  • Improvements of Antijam Performance of Spread-Spectrum Systems

    Publication Year: 1983 , Page(s): 803 - 808
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (528 KB)  

    The present paper gives theoretical analysis and simulation tests of a proposed external circuit connection for enhancing the performance of spread-spectrum (SS) systems in the presence of continuous wave (CW) interference. This connection is an adaptive notch filter. It consists of a hard limiter, a phase-locked-loop (PLL) tracking the CW interference yielding a first estimate, an adaptive two-quadrature weighted channel, and linear combiner producing a more accurate estimate of the CW interference. The simulation tests of this connection give, in general, performances superior to previous authors' results for certain ranges of signal-to-noise ratio. View full abstract»

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  • A Procedure for Optimal Dimensioning of Trunk Groups While Serving Two Traffic Loads with Different Grade of Service

    Publication Year: 1983 , Page(s): 794 - 799
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (504 KB)  

    In this paper we have developed a procedure for optimal dimensioning of trunk groups which serve two traffic loads with different grades of service prescribed. Owing to the overflow character of traffic in the common part of the trunk group, the Wilkinson equivalent random method was used and algorithms for determining necessary traffic parameters were developed. This procedure and the procedure which presupposes that the traffic in the common part of the trunk group is Poissonian have been compared. View full abstract»

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  • The Effects of Noise Correlation and Power Imbalance on Terrestrial and Satellite DPSK Channels

    Publication Year: 1983 , Page(s): 750 - 755
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (528 KB)  

    New results are given for the bit error probability for binary DPSK modulation over both terrestrial and satellite channels taking into account noise correlation and power imbalance. The new expressions are remarkably simpler than their previously published counterparts. For the terrestrial channel, the results are in closed form in terms of tabulated functions and, for the hard-limiting satellite channel, both in terms of integrals readily evaluated by quadrature and in terms of infinite series. Using the results, it is shown that the error rate does not depend on the noise correlation (down-link in the satellite case) so long as the a priori symbol probabilities are equal, thereby solving an "open problem" posed by Lee, French, and Hong. Also, the satellite case in which each of the up-link and down-link channels contains nonzero noise correlations is briefly treated. View full abstract»

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  • Spectral Analysis and Implementation of Duobinary FSK Systems Working at High Bit Rates

    Publication Year: 1983 , Page(s): 811 - 816
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    A new modulation technique for nonperiodic data is presented. Binary data, coded by means of the duobinary technique, modulate a voltage controlled oscillator (VCO). The system has a very simple structure and is capable of transmitting data having a variable bit rate about twice the carrier (VCO) frequency. The resulting spectrum, centered around the VCO frequency, could be as narrow as 0.3 times the bit rate. Telephone line tests show that this technique offers a promising low-cost solution to voice-grade modems. View full abstract»

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  • A Multi-Bit-Rate Substitute-Communication System with High Call-Carrying Capacity

    Publication Year: 1983 , Page(s): 799 - 803
    Cited by:  Papers (1)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (512 KB)  

    A multi-bit-rate substitute-communication system (MSCS) is an efficient means to achieve higher call-carrying capacity in a congested network. When a trunk line is congested with a large amount of traffic, MSCS makes subscribers communicate by a lowerbit-rate medium, even though they request higher-bit-rate forms. This limitation is made when the number of idle basic channels is less than or equal to the predetermined system constant. This paper describes the control method, traffic characteristics, and concrete traffic design method, using a dual-bit-rate class (64 kbits/s, 8 kbits/s) model. It is found that the MSCS carries about five times as many calls as a conventional network without the MSCS. View full abstract»

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  • BTC Image Coding Using Median Filter Roots

    Publication Year: 1983 , Page(s): 784 - 793
    Cited by:  Papers (42)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2608 KB)  

    In this paper we source encode the truncated block used in block truncation coding. It is shown that the truncated block is well approximated by wide-sense Markoff statistics; a signal having these characteristics has a high probability of belonging to the root signal set of median filters. Because the root signal space is much smaller than the binary space, it takes fewer bits to specify the truncated block in the root signal space, obtaining in this manner rate compression. Using two-dimensional filtering we can reduce the standard BTC rate of 1.63 bits/pel to 1.31 bits/pel. Using one-dimensional filtering along with a trellis encoder, rates close to 1.1 bits/pel are obtained with this fixed-length coding method. View full abstract»

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  • Stability and Optimization of the CSMA and CSMA/CD Channels

    Publication Year: 1983 , Page(s): 763 - 774
    Cited by:  Papers (35)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1072 KB)  

    A comprehensive study of the stability and optimization of the infinite population, slotted, nonpersistent CSMA and CSMA/ CD channels is presented. The approach to both stability and performance optimization differs significantly from previous work, and provides a number of new results including robustness in stability and performance in the presence of channel and control parameter variations. It is first shown that both channels are unstable under the usual assumption of random retransmission delay. Pake's lemma is then applied to study the properties of a type of distributed retransmission control which provides stable channels. Basic results are in the form of inequalities which define stability regions in the space of channel and control parameters, and further permit one to specify controls which maximize channel throughput as a function of packet length and CD time with stability guaranteed. The delay versus throughput characteristic for the stabilized channels is derived and used to demonstrate the performance achievable with these channels. View full abstract»

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  • Distributions of the Two-Dimensional DCT Coefficients for Images

    Publication Year: 1983 , Page(s): 835 - 839
    Cited by:  Papers (196)  |  Patents (37)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (904 KB)  

    For a two-dimensional discrete cosine transform (DCT) image coding system, there have been different assumptions concerning the distributions of the transform coefficients. This paper presents results of distribution tests that indicate that for many images the statistics of the coefficients are best approximated by a Gaussian distribution for the DC coefficient and a Laplacian distribution for the other coefficients. Furthermore, from a simulation of the DCT coding System it is shown that the assumption that the coefficients are Laplacian yields a higher actual output signal-to-noise ratio and a much better agreement between theory and simulation than the Gaussian assumption. 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