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Communications, IEEE Transactions on

Issue 9 • Date September 1984

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Displaying Results 1 - 19 of 19
  • [Front cover and table of contents]

    Page(s): 0
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    Freely Available from IEEE
  • When less is more: where the Communications Society's publications are headed

    Page(s): 989
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    Freely Available from IEEE
  • Comment on "Optimal Design of PLL with Two Seperate Phase Detectors"

    Page(s): 1056 - 1058
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    This correspondence comments on a recent paper by Heiman and Bar-Ness. In the paper the authors propose a two-channel PLL and pursue an optimization analysis of the proposed configuration. They base the analysis on Viterbi's equivalent noise model. In our comment it is shown that their application of the model suffers from a fundamental flaw. Difficulties in the physical interpretation of the results are demonstrated. View full abstract»

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  • Comments on "An Efficient SS/TDMA Time Slot Assignment Algorithm"

    Page(s): 1061 - 1065
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    The time slot assignment algorithm presented in the above paper needs certain improvements for it to be an efficient one. In this correspondence, the necessary improvements are incorporated and an improved SS/TDMA time slot assignment algorithm is presented. The new algorithm is compared to the old one and the computer simulation exhibits a better performance of the present algorithm. View full abstract»

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  • [Back cover]

    Page(s): 0
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    Freely Available from IEEE
  • Vector Quantizer Design for Memoryless Gaussian, Gamma, and Laplacian Sources

    Page(s): 1065 - 1069
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    Locally optimum vector quantizer (VQ) designs are presented for memoryless Gaussian, gamma, and Laplacian sources. For Gaussian sources, low (2-6) dimensional vector quantization provides relatively little improvement in mean-squared error (MSE) compared to the minimum mean-squared error (MMSE) scalar quantizer. For Laplacian or gamma sources, however, significant improvement in MSE is available with vector quantization. The Laplacian and gamma 6 bit, sixdimensional vector quantizers achieve, respectively, improvements of 2 and 4.5 dB over the corresponding scalar MMSE quantizer distortions. View full abstract»

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  • Authors' Reply

    Page(s): 1058 - 1060
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    In this correspondence we prove that the optimization process used in the paper leads to bounded optimal phase detectors. The bounds can be applied in normalizing the functions of these detectors, rendering Meidan's argument invalid. View full abstract»

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  • Application of the CCIR Bit Error Ratio Recommendation to Real Digital Radio Paths

    Page(s): 1060 - 1061
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    The CCIR (International Radio Consultative Committee) has published a recommendation on the "Allowable bit error ratios at the output of the hypothetical reference digital path for radio-relay systems for telephony" (Recommendation 594). It has been normal practice to augment such a recommendation on performance with a corresponding recommendation for so-called real digital paths, as discussed in CCIR Report 930. This correspondence proposes and justifies the form that such a recommendation could take. View full abstract»

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  • Synchronizability of a General Class of PCM Formats, Including NRZ, Manchester, and Miller Coding

    Page(s): 1020 - 1024
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    This paper deals with a general class of PCM formats, which includes the well-known NRZ, Manchester, and Miller coding. We show that the Cramér-Rao lower bound on the mean-square error, resulting from a synchronizer which estimates the delay of a noisy PCM waveform, is inversely proportional to a quantity which depends on the PCM format only. This quantity is termed the "synchronizability" of the PCM format. For the general class of PCM formats we consider in this paper, we obtain as a simple result that the synchronizability equals four times the mean number of zero-crossings of the PCM waveform during one symbol period. Numerical results are presented for NRZ, Manchester, and Miller coding. View full abstract»

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  • The Weight Spectra of Some Short Low-Rate Convolutional Codes

    Page(s): 1050 - 1053
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    This paper reports the results of a computer analysis of the distance properties of some of the best known rate 1/2, 1/3, and 1/4 codes to constraint length 14. The data include the truncated weight distributions of the codewords belonging to the incorrect subset which specifies the performance of the Viterbi algorithm as well as the minimum asymptotic growth rate of the weights of unmerged codewords which has been conjectured to be related to the length of error events produced by Viterbi decoders. View full abstract»

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  • An A, B-Polar Approach for Multimode Polarization Analysis in Satellite Communications

    Page(s): 1045 - 1049
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    This paper describes a convenient method of polarization analysis for a circular multimode aperture antenna by decomposing the field distribution into two components calledA,B-polar. The new idea in this technique is the separation of theA,B-polar for field expression into a rotationally symmetric magnitude function and an orientation function independent of the antenna off-axis. This leads to easily sketched figures of the multimode polarization patterns which give a clear physical picture on their effects and applications. Several examples are done in the context of the frequency reuse capabilities of earth-station antennas. View full abstract»

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  • Adaptive Multiplication-Free Transversal Equalizers with Application to Digital Radio Systems

    Page(s): 1025 - 1033
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    Recently, multiplication-free digital filters have been proposed for different applications to digital radio systems and signal processing. The absence of multiplication is obtained by constraining each coefficient to be sum of powers of two. In this way, multipliers are substituted by shift registers and, if appropriate, some adders. The optimal power-of-two coefficients must be computed through a nonlinear optimization procedure. Until now the problem of adapting the power-of-two coefficients of base band transversal equalizers in the case of time-varying channels had not been considered. In this paper two algorithms are proposed to cope with this problem and are compared from the viewpoint of complexity, accuracy, and convergence speed. As an application example, transmission of a biphase PSK digital radio system over a multipath fading channel is considered. View full abstract»

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  • On the Probability of Undetected Error for the Maximum Distance Separable Codes

    Page(s): 998 - 1006
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    In this paper we investigate the performance of maximum-distance-separable codes with symbols fromGF(q)when they are used for pure error detection or for simultaneous error correction and detection over aq-input andq-output discret memoryless channel with symbol error probability ε. First we show that the probability of undetected error for an MDS code used for pure error detection is upper bounded byq^{-r}and decreases monotonically as εdecreases from(q - 1)/qto 0, whereris the number of parity-check symbols of the code. Then we show that the probability of undetected error for an MDS code used for correctingtor fewer symbol errors is upper bounded byq^{-r} Summin{i=0}max{t}(min{i} max{n})(q - 1)^{i}and decreases monotonically as ε decreases from(q - 1)/qto 0. These results show that the MDS codes are effective for both pure error detection and simultaneous error correction and detection. View full abstract»

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  • An Analytic Model for Flow Control Schemes in Communication Network Nodes

    Page(s): 1013 - 1019
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    A Markov model is developed for a message processing node with batch arrivals and various flow control schemes. In particular, a credit allocation pacing control mechanism, previously modeled only by simulation, is represented analytically. The primary application is the network-independent flow control of messages between networks which may have quite different characteristics, via a gateway, but the approach is sufficiently general for modeling many servers or whole subnetworks in any queueing system. A closed form solution to the model's balance equations cannot be found, and direct solution is impracticable due to their number. However, by identifying invariants and making physically realistic approximations, the size of the state space is reduced to such an extent that direct numerical solution does become viable. In particular, the credit allocation scheme is shown to be equivalent to the node's operation in different modes, each with its own buffer capacity, so that credit control need not be modeled explicitly, and no approximation is incurred. Accuracy is assessed by comparison with the results of explicit simulations of a selection of nodes of this type with various parameterizations. Finally, we suggest applications for the model in the assessment and comparison of performance under various congestion control schemes and propose some new stabilizing mechanisms. View full abstract»

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  • A Fundamental Lower Bound on the Performance of Practical Joint Carrier and Bit Synchronizers

    Page(s): 1007 - 1012
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    In this paper we derive a fundamental lower bound on the linearized mean-square phase and time delay errors resulting from a practical synchronizer operating on a carrier-modulated PAM waveform which is corrupted by stationary Gaussian noise. Our bound applies to a large class of synchronizers and, unlike the linearized performance itself, it is easily evaluated from the modulation format, the baseband PAM pulse shape, the additive noise spectrum, and the synchronizer's closedloop transfer function matrix. View full abstract»

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  • Optimum and Suboptimum Space-Diversity Detection of Weak Signals in Non-Gaussian Noise

    Page(s): 990 - 997
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    The structure of the locally optimum space-diversity detector for coherent detection of a bandpass signal subject to amplitude fluctuations in the presence of narrow-band non-Gaussian noise is derived and its large-sample performance is evaluated. For easy implementation a suboptimum structure is proposed. It consists of local detectors performing independent local decisions and of a central processor that, working according to simple logical schemes (OR or AND), performs the global decision based on the local ones. Numerical results and a comparison between the performances of both proposed structures are presented and discussed. View full abstract»

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  • Note on a Class of Codes Introduced by Séguin, Allard, and Bhargava

    Page(s): 1053 - 1056
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    In this correspondence, we apply a theorem in finite geometry to obtain an improvement of the codes recently introduced by Séguin, Allard, and Bhargava to provide error protection for data in the ASCII format. Our construction yields a fast decoding algorithm. View full abstract»

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  • Point-To-Multipoint Communication Over Broadcast Links

    Page(s): 1034 - 1044
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    In this paper we study some link control protocols for use in point-to-multipoint communication over broadcast links. We concentrate on automatic repeat request protocols of the go-back-Ntype and define, analyze, and compare three such protocols. A major contribution of this paper is a relatively simple protocol which is easy to implement and performs very well under a wide range of conditions. Our analytical models show that this protocol performs considerably better than the other go-back-Nprotocols, particularly in environments with a large number of receivers. 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.

 

 

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Robert Schober
University of British Columbia