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Communications, IEEE Transactions on

Issue 3 • Date Mar 2000

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Displaying Results 1 - 20 of 20
  • Multicomponent AM-FM demodulation via periodicity-based algebraic separation and energy-based demodulation

    Page(s): 473 - 490
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    Previously investigated multicomponent AM-FM demodulation techniques either assume that the individual component signals are spectrally isolated from each other or that the components can be isolated by linear time-invariant filtering techniques and, consequently, break down in the case where the components overlap spectrally or when one of the components is stronger than the other. In this paper, we present a nonlinear algorithm for the separation and demodulation of discrete-time multicomponent AM-FM signals. Our approach divides the demodulation problem into two independent tasks: algebraic separation of the components based on periodicity assumptions and then monocomponent demodulation of each component by instantaneously tracking and separating its source energy into its amplitude and frequency parts. The proposed new algorithm avoids the shortcomings of previous approaches and works well for extremely small spectral separations of the components and for a wide range of relative amplitude/power ratios. We present its theoretical analysis and experimental results and outline its application to demodulation of cochannel FM voice signals View full abstract»

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  • Upper-bound performance of a wide-band adaptive modem

    Page(s): 367 - 369
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    Adaptive modulation is applied in conjunction with a decision-feedback equalizer (DFE) in order to mitigate the effects of the slowly varying wide-band multipath Rayleigh fading channel in a noise-limited environment. An upper-bound mean bit-error rate and bits per symbol performance is introduced for this scheme by utilizing the pseudo signal-to-noise ratio at the output of the DFE in order to switch the modulation schemes on a burst-by-burst basis View full abstract»

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  • Convergence analysis of the least squares constant modulus algorithm in interference cancellation applications

    Page(s): 491 - 501
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    The convergence behavior of the least squares constant modulus (CM) algorithm in an adaptive beamforming application is examined. It is assumed that the desired signal and the interference are uncorrelated. The improvement in output signal-to-interference ratio (SIR) with each iteration of the algorithm is predicted for several different signal environments. Deterministic results are presented for an environment containing two complete sinusoids. Probabilistic results are presented for a CM desired signal with a CM interferer and with a Gaussian interferer. The asymptotic improvement in output SIR as the output SIR becomes high is also derived. The results of Monte Carlo simulations using sinusoidal, frequency modulation, and quadrature phase-shift keying signals are included to support the derivations View full abstract»

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  • The equivalence of two unified solutions for optimum space-time processing

    Page(s): 370 - 372
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (76 KB)  

    Ariyavisitakul et al. (IEEE Trans. Commun., vol.47, p.1073-83, 1999 July) provided a unified analysis of optimum space-time processors based on the following two analytical diversity receiver models: 1) a general model-with a linear filter on each diversity branch, and 2) a “matched filter” model-with a bank of matched filters on each branch, followed by common filter. Closed-form results were given for each receiver model, in terms of the minimum mean-square-error or maximum signal-to-noise ratio solutions for different types of equalizers, including a linear equalizer (LE), a decision-feedback equalizer (DFE), and a maximum-likelihood sequence estimator (MLSE). Although we implied that the two receiver models lead to the same optimum solutions, this requires some proof that is not directly obtainable from the results we presented. We therefore provide such a proof in the present paper for the completeness of the overall unified analysis View full abstract»

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  • Extensions to an authentication technique proposed for the global mobility network

    Page(s): 373 - 376
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (88 KB)  

    We present three attacks on the authentication protocol that has been proposed for the so-called global mobility network in the October 1997 issue of the IEEE Journal on Selected Areas in Communications. We show that the attacks are feasible and propose corrections that make the protocol more robust and resistant against two of the presented attacks. The aim is to highlight some basic design principles for cryptographic protocols, the adherence to which would have prevented these attacks View full abstract»

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  • Near-far resistant channel estimation for CDMA systems using the linear decorrelating detector

    Page(s): 514 - 524
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (324 KB)  

    The well-known linear decorrelating detector (LDD) for direct-sequence code-division multiple-access (CDMA) systems provides near-far resistant performance when the timing of each user is accurately known. Traditional CDMA acquisition techniques suffer from high differences in power levels. The estimation accuracy for a user overwhelmed by stronger ones is likely to be unsatisfactory; at the same time, the interference from a user undergoing acquisition or tracking is not removed by the standard LDD. In this paper, a fully near-far resistant technique for acquisition and tracking for asynchronous CDMA systems applying the LDD is proposed, considering realistic band-limited signals. This technique is based on the adoption of a pair of special sequences equivalent to a dedicated access channel and is shown to provide a relatively fast and robust means to perform channel estimation both in case of single- and multipath channels View full abstract»

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  • Exponential-type bounds on the generalized Marcum Q-function with application to error probability analysis over fading channels

    Page(s): 359 - 366
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    Strict upper and lower bounds of exponential-type are derived for the generalized (mth order) Marcum Q-function which enable simple evaluation of a tight upper bound on the average bit-error probability performance of a wide class of noncoherent and differentially coherent communication systems operating over generalized fading channels. For the case of frequency selective fading with arbitrary statistics per independent fading path, the resulting upper hound on performance is expressed in the form of a product of moment generating functions of the instantaneous power random variables that characterize these paths View full abstract»

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  • Performance analysis of the error-forecasting decoding for interleaved block codes on Gilbert-Elliott channels

    Page(s): 386 - 395
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    This paper investigates the performance of the error-forecasting decoding for an interleaved block code on Gilbert-Elliott channels in terms of the word-error probability, which is the sum of the decoder error and failure probabilities. We derive expressions by constructing several Markov chains, starting from a two-state Markov chain of the Gilbert-Elliott channel model. The derived formulas are examined for an interleaved Reed-Solomon code on solid-density and moderate-density burst error channels. Numerical results indicate that the error-forecasting decoding can significantly improve the performance, particularly on solid-density burst error channels. The optimal depth of interleaving for the error-forecasting decoding is also numerically evaluated View full abstract»

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  • Bandwidth assignment with QoS guarantee in a class of scalable ATM switches

    Page(s): 377 - 380
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (84 KB)  

    This letter addresses issues related to achieving optimal performance in a class of scalable asynchronous transfer mode switches. In particular, we propose an algorithm to implement a multilevel stop-and-go queueing strategy that integrates the routing and scheduling functions. The algorithm provides a tight delay bound and ensures that desirable traffic characteristics are preserved when cells traverse across the switch View full abstract»

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  • On runlength-limited coding with DC control

    Page(s): 351 - 358
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (232 KB)  

    Constructions are presented of finite-state encoders for certain (d,k) runlength-limited (RLL) constraints with direct current control. In particular, an example is provided for a rate 8:16 encoder for the (2,10)-RLL constraint that requires no look-ahead in decoding, thus, performing favorably compared to the EFMPlus code used in the DVD standard View full abstract»

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  • Degradation of availability performance in dual-polarized satellite communications systems

    Page(s): 465 - 472
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (136 KB)  

    Dual-polarized operation of satellite communications channels allows for an efficient use of the radio spectrum. A method for evaluating the availability of Ku- and Ka-band dual-polarized digital systems is described. It is based on long-term measurements of slant-path attenuation and depolarization caused by the troposphere and of their joint occurrence. The additional degradation of dual-polarized system availability performance with respect to single polarization operation is assessed, and its dependence on major link and system parameters is highlighted. It appears that satellite links characterized by high-frequency, low elevation angle, circular polarization, and high-level modulation schemes are particularly affected by the depolarization-induced interference. In that case, doubling their capacity by dual-polarization frequency reuse reduces dramatically their availability, assuming a fixed link margin, or alternatively requires prohibitive link margins to meet a given availability objective View full abstract»

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  • An MGF-based performance analysis of generalized selection combining over Rayleigh fading channels

    Page(s): 401 - 415
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    Using the notion of the “spacing” between ordered exponential random variables, a performance analysis of the generalized selection combining (GSC) diversity scheme over Rayleigh fading channels is presented and compared with that of the conventional maximal-ratio combining and selection combining schemes. Starting with the moment generating function (MGF) of the GSC output signal-to-noise ratio (SNR), we derive closed-form expressions for the average combined SNR, outage probability, and average error probability of a wide variety of modulation schemes operating over independently, identically distributed (i.i.d.) diversity paths. Because of their simple form, these expressions readily allow numerical evaluation for cases of practical interest. The results are also extended to the case of non-i.i.d. diversity paths View full abstract»

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  • Fading correlation and its effect on the capacity of multielement antenna systems

    Page(s): 502 - 513
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (292 KB)  

    We investigate the effects of fading correlations in multielement antenna (MEA) communication systems. Pioneering studies showed that if the fades connecting pairs of transmit and receive antenna elements are independently, identically distributed, MEAs offer a large increase in capacity compared to single-antenna systems. An MEA system can be described in terms of spatial eigenmodes, which are single-input single-output subchannels. The channel capacity of an MEA is the sum of capacities of these subchannels. We show that the fading correlation affects the MEA capacity by modifying the distributions of the gains of these subchannels. The fading correlation depends on the physical parameters of MEA and the scatterer characteristics. In this paper, to characterize the fading correlation, we employ an abstract model, which is appropriate for modeling narrow-band Rayleigh fading in fixed wireless systems View full abstract»

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  • Low timing sensitivity receiver structures for CAP

    Page(s): 396 - 400
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (164 KB)  

    Carrierless amplitude and phase (CAP) is one of the modulation schemes that has been proposed to accomplish the task of transporting high bit-rate data over cheap copper wire pairs. In this paper, we reexamined some CAP receiver structures that have been proposed in the literature and showed that the modified quadrature amplitude modulation receiver can offer a significant advantage over the other receiver structures through its greater immunity to timing phase errors. Our recommendation is based on an analysis of the eye diagram of a received CAP signal View full abstract»

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  • Statistical analysis and characterization of the indoor propagation channel

    Page(s): 455 - 464
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (276 KB)  

    This paper presents statistical analysis of data obtained by measuring narrowband path loss at DECT (digital enhanced cordless telecommunications) frequency (1.89 GHz) in an indoor environment. Specific goodness-of-fit tests are applied to the data. The tests assess whether the data generating source belongs to a known family of random variables. Results obtained support that local path-loss distribution can be represented as Weibull or Nakagami in most environments. The close resemblance between such distributions and Rice distribution (with Rayleigh as a special case) confirms that Rice/Rayleigh description of fading can be applied to indoor environments. That similarity leads to a general, simple, approximate expression for the cumulative distribution function of the signal-to-interference ratio. The expression can be used without limitations to the number and the parameters of the Rice interferers View full abstract»

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  • Chase-type and GMD coset decodings

    Page(s): 345 - 350
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (152 KB)  

    In this letter, Chase decoding algorithms are generalized into a family of bounded distance decoding algorithms, so that the conventional Chase algorithm-2 and Chase algorithm-3 become the two extremes of this family. Consequently, more flexibility in the tradeoffs between error performance and decoding complexity is provided by this generalization, especially for codes with large minimum distance. Finally this approach is extended to decoding with erasures View full abstract»

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  • Outage analysis in mobile radio systems with generically correlated log-normal interferers

    Page(s): 381 - 385
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (204 KB)  

    A novel methodology is proposed for computing the outage probability in mobile radio systems in the presence of log-normal shadowing. A relevant feature is that the proposed analysis assumes a general correlation for any pair of links. Various approaches are considered to compute the statistics of user signal-to-interference ratio (SIR), namely Schwartz and Yeh's method, Wilkinson's method, and Fenton's method. By a simple reformulation of the problem, these methods can be used to calculate in a straightforward way the parameters of the SIR. The accuracy of the methods is checked in a number of situations of interest. Moreover, when the same correlation is assigned to any pair of links, the novel analysis is more accurate than previously proposed approaches View full abstract»

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  • A framework for analyzing the user membership in cellular CDMA networks

    Page(s): 442 - 454
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (308 KB)  

    A theoretical framework is developed to analyze the user membership in cellular networks. The main interest is on code-division multiple-access (CDMA) networks, although the validity of the proposed approach is not restricted to these networks. The membership of a user terminal to a certain base station (BS) is established if the local mean attenuation to this BS is the lowest one among all surrounding BSs. The estimate of local mean attenuation on the radio links from a mobile terminal to each of the surrounding BSs is carried out through proper filtering of the sequences of received signal strength measurements taken on broadcast signals at regular time intervals. In CDMA networks, pilot channels can be considered, while broadcast control channels can be generically considered in narrow-band systems. A decision is made each time on whether the terminal is to be assigned to its “current” BS or if it would be better served by a different BS. Two performance measures are considered: the probability that the best BS is not selected and the average number of membership switchings per time unit. A channel model with log-normal shadowing and fast fading superimposed is considered. Analytical expressions for the above-mentioned performance measures are derived in a general system scenario. From numerical results, it is seen that a proper choice of filter parameters is required to achieve the lowest values for both performance measures. Moreover, these values are not negligible when the mobile terminal is close to a boundary cell region. The obtained results are considered to be of interest in handover and power control algorithms View full abstract»

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  • Hierarchical digital modulation classification using cumulants

    Page(s): 416 - 429
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (380 KB)  

    A simple method, based on elementary fourth-order cumulants, is proposed for the classification of digital modulation schemes. These statistics are natural in this setting as they characterize the shape of the distribution of the noisy baseband I and Q samples. It is shown that cumulant-based classification is particularly effective when used in a hierarchical scheme, enabling separation into subclasses at low signal-to-noise ratio with small sample size. Thus, the method can be used as a preliminary classifier if desired. Computational complexity is order N, where N is the number of complex baseband data samples. This method is robust in the presence of carrier phase and frequency offsets and can be implemented recursively. Theoretical arguments are verified via extensive simulations and comparisons with existing approaches View full abstract»

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  • Theoretical analysis and performance of OFDM signals in nonlinear AWGN channels

    Page(s): 430 - 441
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (364 KB)  

    Orthogonal frequency-division multiplexing (OFDM) baseband signals may be modeled by complex Gaussian processes with Rayleigh envelope distribution and uniform phase distribution, if the number of carriers is sufficiently large. The output correlation function of instantaneous nonlinear amplifiers and the signal-to-distortion ratio can be derived and expressed in an easy way. As a consequence, the output spectrum and the bit-error rate (BER) performance of OFDM systems in nonlinear additive white Gaussian noise channels are predictable both for uncompensated amplitude modulation/amplitude modulation (AM/AM) and amplitude modulation/pulse modulation (AM/PM) distortions and for ideal predistortion. The aim of this work is to obtain the analytical expressions for the output correlation function of a nonlinear device and for the BER performance. The results in closed-form solutions are derived for AM/AM and AM/PM curves approximated by Bessel series expansion and for the ideal predistortion case 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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Editor-in-Chief
Robert Schober
University of British Columbia