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Communications, IEEE Transactions on

Issue 2 • Date February 1985

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Displaying Results 1 - 15 of 15
  • [Front cover and table of contents]

    Page(s): 0
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    Freely Available from IEEE
  • [Back cover]

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    Freely Available from IEEE
  • Nonparametric Receiver for FH-MFSK Mobile Radio

    Page(s): 178 - 184
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (520 KB)  

    Various parametric receivers such as the maximum likelihood and the hard-limiter have been analyzed for their performance in decoding the frequency hopped multilevel FSK (FH-MFSK) messages in mobile environment. Here, some nonparametric receivers such as the maximum rank sum receiver (MRSR) and the reduced rank sum receiver (RRR) are considered. RRR and MRSR are nearly identical in performance but the former is much simpler to implement. The results indicate that RRR is a competing alternative to the parametric receivers. View full abstract»

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  • A Simple Algorithm for the Control of Rearrangeable Switching Networks

    Page(s): 169 - 171
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (352 KB)  

    A simple algorithm for the control of rearrangeable switching networksnu(n, n, r)is given. This algorithm makes it possible to compute the switch settings that implement a given Permutation. The algorithm takes serial timeO(nr^{2})and consists of one phase, i.e., it does not require iterations. The version of the algorithm which can be used for group switching is also presented. View full abstract»

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  • A Class of Efficient Contention Resolution Algorithms for Multiple Access Channels

    Page(s): 145 - 151
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (816 KB)  

    A discrete time multiaccess channel is considered where the outcome of a transmission is either "idle," "success," or "collision," depending on the number of users transmitting simultaneously. Messages involved in a "collision" must be retransmitted. An efficient access allocation policy is developed for the case where infinitely many sources generate traffic in a Poisson manner and can all observe the outcomes of the previous transmissions. Its rate of success is 0.48776. Modifications are presented for the cases where the transmission times depend on the transmission outcomes and where observations are noisy. View full abstract»

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  • A Condition for Stable Minimum-Bandwidth Line Codes

    Page(s): 152 - 157
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (600 KB)  

    By generalizing a concept on a power spectral zero at the Nyquist frequency, a condition for the line codes' capability to signal with the minimum bandwidth is established. From the condition, lower bounds of eyewidth are obtained for various values of a new system parameter called intersymbol interference sum variation (ISV). As an application of the condition, the nonminimum-bandwidth bipolar code is modified to a minimum-bandwidth code, which can be directly used in conventional bipolar signaling systems with increased bandwidth efficiency. View full abstract»

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  • A Note on "Modulation Methods Related to Sine Wave Crossings"

    Page(s): 177 - 178
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    In this correspondence we show that the above paper is a rediscovery of what was known since 1973 [1]. The contents of the paper have been published in various forms in the literature. The more general case of a periodic wave crossing has already been considered, which covers the special case of a sine wave crossing. View full abstract»

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  • Blocking Probability of Noninteger Groups with Trunk Reservation

    Page(s): 113 - 120
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (472 KB)  

    A model for computing the blocking probability in circuitswitched networks operating with trunk reservation is extended to the case of noninteger trunk numbers. This generalization is required if the model is to be used in network optimization algorithms, which are generally evaluated over the reals. A simple extension is first presented, and shown to be numerically unstable over some values of the parameters. A recursive approach is then explained that is both robust and efficient for an integer number of reserved trunks and arbitrary parameters. The model is finally extended to arbitrary trunk numbers, and an efficient and robust algorithm is proposed. View full abstract»

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  • Computations of DSI (TASI) Overload as a Function of the Traffic Offered

    Page(s): 188 - 190
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    This paper presents an analysis of the performance of a digital speech interpolation (DSI) system as a function of the traffic offered to the system. We assume that the DSI overload degradation occurs as clipping or freezeout. This is identical to TASI freezeout. Unlike conventional analysis, which assumes all of the trunks entering the DSI system are busy all the time, we calculate the freezeout fraction as a function of the traffic offered. In almost all practical situations the freezeout fraction, computed based on traffic assumptions, is considerably less than that computed assuming all trunks are busy. When a DSI system is used to compressNtrunks down intocchannels, there is always a tradeoff between the blocking probability in the trunk group and the degradation introduced by the DSI system. This tradeoff depends on the traffic offered and is explored in this paper. View full abstract»

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  • The Role of AM-to-PM Conversion in Memoryless Nonlinear Systems

    Page(s): 139 - 144
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    A generalized proof is presented that AM-to-PM conversion can only degrade, never improve, the intermodulation-noise performance of memoryless nonlinear systems with random input signals having even probability density functions, and a measure of degradation is defined. It is also shown for such signals that AM-to-PM conversion causes a deterministic constant phase shift to be added to the argument of the signal component at the output but has no other effect on its phase. This class of inputs includes one or the sum of several PSK signals, as well as large ensembles that can be modeled as Gaussian noise. The latter are dealt with by using Bussgang's theorem on input-output cross correlation. In the proof, Bussgang's theorem is extended to the complex case, to include phase as well as amplitude nonlinearities, yielding a complex version of the theorem. For Gaussian inputs it is shown that the undistorted signal and the intermodulation noise at the output of such systems are uncorrelated. View full abstract»

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  • Double Loop Network Architectures--A Performance Study

    Page(s): 185 - 187
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    Single loop networks tend to become unreliable and suffer from poor performance when the number of nodes in the network becomes large. One approach to increasing reliability and improving performance is to use a double loop. In this paper, the performance (using analytical and simulation models) of a class of highly reliable double loop network architectures is presented. The richer topology of double loop networks allows more sophisticated routing algorithms to be used. Several routing algorithms are studied, including: fixed, adaptive to failure, and fully adaptive to failure and traffic load conditions. View full abstract»

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  • Optimum Linear Equalization in Digital Fiber-Optic Systems

    Page(s): 158 - 168
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    We exhibit an optimum linear equalizer that maximizes the signal-to-noise ratio while mitigating the effects of intersymbol interference, in the case of dispersion limited operation of a digital fiber-optic transmission system. The simultaneous presence of signal-dependent noise, thermal noise, and blue noise reduces the problem to seeking a solution of an inhomogeneous linear second-order differential equation with a time-varying coefficient. Relative to detection in a channel free of intersymbol interference, we calculate power penalties at different transmission rates and compare the results to those of the integrate-and-dump and the raised-cosine-output systems. View full abstract»

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  • An Approximate Statistical Analysis of the Widrow LMS Algorithm with Application to Narrow-Band Interference Rejection

    Page(s): 121 - 130
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (928 KB)  

    The Widrow LMS algorithm is considered for the implementation of an adaptive prewhitening filter in a direct-sequence (DS) spread-spectrum receiver. Exact expressions for the steady-state tapweight covariance matrix and resulting average excess mean square error are developed for the real LMS algorithm when the input contains a random binary sequence (used to model a pseudonoise spreading sequence). It is shown here that the output samples of the adaptive filter possess approximately Gaussian statistics under the conditions of slow convergence and a large number of filter taps. Using this approximation, expressions for the resulting bit error rate (BER) when the adaptive algorithm is used to suppress a fading gone jammer are developed, and numerical results obtained from these expressions are compared to simulation results for the DS receiver. View full abstract»

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  • New Short Constraint Length, Rate 1/N Convolutional Codes Which Minimize the Required SNR for Given Desired Bit Error Rates

    Page(s): 171 - 177
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    New, good (K, 1/N) convolutional codes are tabulated for3 leq K leq 7and2 leq N leq 8, which were selected based on the criterion of minimizing the required signal-to-noise ratio (SNR) for given desired bit error rates (BER). A transfer function upper bound was used to find the BER performance. Partial searches were performed using the idea that "good codes generate good lower rate codes." The new codes save signal energy up to 0.4 dB compared to previously reported codes of the same parameters. View full abstract»

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  • Properties of Frequency Difference Detectors

    Page(s): 131 - 138
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (728 KB)  

    Among other applications, frequency-tracking loops are employed in digital-data receivers, either as a frequency-acquisition aid for phase-locked coherent reception, or as the sole carrier-frequency control for noncoherent reception. This article provides details of design and performance of the frequency-difference detector that lies at the heart of the loop. 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