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Communications, IEEE Transactions on

Issue 12 • Date December 1985

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Displaying Results 1 - 17 of 17
  • [Front cover and table of contents]

    Publication Year: 1985 , Page(s): 0
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    Freely Available from IEEE
  • Editorial

    Publication Year: 1985 , Page(s): 1233
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    Freely Available from IEEE
  • [Back cover]

    Publication Year: 1985 , Page(s): 0
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    Freely Available from IEEE
  • Noise Loading Analysis in FDM Systems

    Publication Year: 1985 , Page(s): 1319 - 1323
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (464 KB)  

    This paper investigates the characterization of nonlinear distortion produced in FDM systems under high-frequency operation, by using noise loading techniques. By employing a general Volterra-based model, the paper develops an appropriate noise loading technique for the assessment of nonlinear distortion in such wide-band transmission systems. The advantage of using Volterra series representation is that it takes account of system nonlinear-memory behavior in a combined formulation. View full abstract»

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  • Performance Analysis of PCM/ADPCM Transcoding Systems

    Publication Year: 1985 , Page(s): 1303 - 1308
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (544 KB)  

    In this paper, the performances of PCM/ADPCM transcoding systems are analyzed. The coders studied are the 64 kbit/s PCM with μ-255 companding law and the 32 kbit/s ADPCM proposed by Cummiskey et al. The theoretically predicted performance agrees closely with the results of computer simulation for a wide range of input signal level. According to the results, the performance degradation resulting from the code conversion process appears to be minimal for the single tandem case. However, for the case of multiple tandem code conversions, the performance becomes significantly degraded as the number of tandem coders increases. The overall performance of the transcoding system depends largely on the performance of the coder that is inferior to the other coder being cascaded. View full abstract»

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  • Negatively Correlated Diversity Branches Using Various Modulation Methods and Maximal Ratio Combining

    Publication Year: 1985 , Page(s): 1323 - 1326
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (408 KB)  

    A diversity system using maximal ratio combining, and in which the diversity branches are negatively correlated, is considered. The performance of some digital systems, namely PSK, DPSK, CFSK, and NFSK, are compared. The error probability as a function of frequency differences between the branches is given. Also, error probability averaged over time delay difference τ is given as a function of direct as well as indirect signal-to-noise ratio. The sensitivity of the error probability to the form of the density function of τ is investigated. M th order of diversity is considered, but second- and third-order diversity are specifically analyzed. View full abstract»

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  • Synchronous Tandem Algorithm for 32-kbit/s ADPCM

    Publication Year: 1985 , Page(s): 1309 - 1314
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (648 KB)  

    The synchronous tandem property of nonaccumulation of distortion in tandem-connected ADPCM coders with a 64 kbit/s PCM interface is discussed here. The synchronous tandem algorithm used to provide this property in the steady-state mode is described with a case-by-case analysis, so as to show how the synchronous tandem property is realized in an ADPCM coder. A 32 kbit/s ADPCM coder utilizing this algorithm has been standardized by the CCITT (International Telegraph and Telephone Consultative Committee). The synchronous tandem property of the 32 kbit/s ADPCM coder is of great interest in network applications, because the ADPCM coder appears likely to be introduced into digital networks built partially with existing 64 kbit/s PCM circuits. View full abstract»

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  • Prevention of Store-and-Forward Deadlock in Computer Networks

    Publication Year: 1985 , Page(s): 1258 - 1264
    Cited by:  Papers (30)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (880 KB)  

    Much previous work has been done on the prevention of store-and-forward deadlock in computer networks using buffer reservation. The emphasis has been on reducing the number of reserved buffers necessary in each node. In this paper, we propose a scheme that, for most networks, will guarantee deadlock freedom for any arbitrary routing with a third fewer reserved buffers than the best previously proposed scheme. View full abstract»

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  • The Influence of Phase-Dependent Loop Noise on the Cycle Slipping of Symbol Synchronizers

    Publication Year: 1985 , Page(s): 1234 - 1239
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (512 KB)  

    The spectral density of the loop noise in the equivalent loop model of a symbol synchronizer depends on the phase error. Although this dependence has only a minor influence on the linearized mean-square synchronization error, we demonstrate that it has a major effect on the mean cycle slip time of the symbol synchronizer. A simple approximate expression for the mean cycle slip time is presented, by means of which this effect can be estimated quite accurately. View full abstract»

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  • Augmented Lagrangean Based Algorithms for Centralized Network Design

    Publication Year: 1985 , Page(s): 1247 - 1257
    Cited by:  Papers (10)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1112 KB)  

    Capacitated spanning tree problems appear frequently as fundamental problems in many communication network design problems. An integer programming formulation and a new set of valid inequalities are presented for the linear characterization of the problem. A combination of a subgradient optimization procedure and an augmented Lagrangean-based procedure is used to generate tight lower bounds. The procedure begins with an explicit representation of a subset of the constraints, and the corresponding Lagrangean problem is solved. The solution is examined in order to identify implicit constraints that are violated. Those are added to the Lagrangean problem, forming an expanded problem, and an efficient dual ascent procedure is then applied. When no further improvement is possible through this procedure, a subgradient optimization procedure is invoked in order to further tighten the lower bound value. An exchange heuristic is applied to the nonfeasible Lagrangean solution, in an attempt to generate good feasible solutions to the problem. The procedure has been tested and has generated bounds that are significantly better than ones obtained through previously published procedures. View full abstract»

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  • Low Complexity Carrier Phase Tracking Decoders for Continuous Phase Modulations

    Publication Year: 1985 , Page(s): 1285 - 1290
    Cited by:  Papers (14)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (624 KB)  

    Phase tracking capability is incorporated into two sequence estimation decoders for continuous phase modulations. One decoder employs the Viterbi algorithm; the other uses a reduced-survivor approach proposed earlier by one of the authors [11] for the more bandwidth efficient of these modulations. Computational complexity with the simplest of the joint data/phase algorithms is only marginally greater than that required for the equivalent decoding algorithm employing an externally derived carrier phase reference as supplied by a conventional carrier recovery circuit. Simulations with representative partial response modulations demonstrate the phase synchronization and tracking capabilities of the decoders. High SNR losses relative to an optimal receiver having perfect phase knowledge are found to be small (∼ 1 dB). View full abstract»

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  • Quadrature Vestigial Sideband (QVSB) Data Transmission

    Publication Year: 1985 , Page(s): 1274 - 1280
    Cited by:  Papers (2)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (632 KB)  

    The combined use of quadrature modulation and vestigial sideband filtering is investigated as a means of obtaining a spectrally efficient modulation scheme. The name quadrature vestigial sideband (QVSB) aptly describes the new system, whereby two independent data streams are each VSB modulated into the same passband, but on quadrature related carriers. The inherent interference between the quadrature related channels is shown to be of a controlled form, similar to the intersymbol interference (ISI) in partial response (PR) systems. Techniques suitable for "unwinding" the ISI in PR systems are shown to be also applicable to QVSB. Precoding with bit-by-bit, decoding, nonoptimum and optimum probablistic decoding are investigated. The latter method results in only a 1.2 dB E_{b}/N_{0} degradation, at P_{b} = 10^{-5} , compared to coherent binary phase shift keying (BPSK), although up to a fourfold increase in spectral efficiency can be obtained. View full abstract»

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  • Performance of MRC Diversity Systems for the Detection of Signals with Nakagami Fading

    Publication Year: 1985 , Page(s): 1315 - 1319
    Cited by:  Papers (87)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (424 KB)  

    Bit error rate (BER) is analyzed theoretically for diversity reception in Nakagami fading environment using an M -branch maximal ratio combiner (MRC). Coherent and incoherent reception of frequency shift keying (FSK) are considered, using the multiple branch diversity system for both identical and different diversity branch fading parameters. The effect of correlation is also considered for the dual diversity case. The results are extended to include coherent phase shift keying (CPSK) and differential phase shift keying (DPSK). View full abstract»

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  • Performance of Voice/Data Integration on a TDM System

    Publication Year: 1985 , Page(s): 1265 - 1273
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (840 KB)  

    Data queueing is of primary concern in a voice/data integrated TDM system. The data queueing model is represented in the discrete-time domain with multiple servers and voice is given a higher priority than data. The data arrival process is assumed to be Poisson and the voice arrival process is characterized by a Markov chain. The correlation coefficient of the number of on voice calls between consecutive frames is used to measure the correlation behavior of the voice process. While the generating function approach may be used to analyze the queueing process, it involves the evaluation of a large number of boundary terms. On the assumption that the voice traffic consists of N i.i.d. two-state Markov chains, we derive a simple expression for the mean queue size as a function of two variables in the form of the traffic departure processes. The results clearly reveal a significant influence of the correlation coefficient on the data queueing process. Then, an approximate analysis based on the departure processes is introduced. The numerical and simulation results indicate that this approximate approach yields reasonably accurate results. View full abstract»

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  • Fixed and Adaptive Predictors for Hybrid Predictive/Transform Coding

    Publication Year: 1985 , Page(s): 1291 - 1302
    Cited by:  Papers (16)  |  Patents (61)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1848 KB)  

    Hybrid predictive/transform coding is studied. The usual formulation is to first apply a unitary transform and then code the transform coefficients with independent DPCM coders, i.e., the prediction is performed in the transform domain. This structure is compared to spatial domain prediction, where a difference signal is formed in the spatial domain and then coded by a transform coder. A linear spatial domain predictor which minimizes the mean square prediction error also minimizes the mean square of each transform coefficient. The two structures are equivalent if the transform domain prediction scheme is extended to a more general predictor. Hence, the structure that gives the easiest implementation can be chosen. The spatial domain structure is preferred for motion compensation and for line interlaced video signals. Interframe hybrid coding experiments are performed on interlaced videophone scenes using an adaptive transform coder. Motion compensation gives a rate reduction of 25-35 percent compared to frame difference prediction with the same mean square error. The subjective advantage is even greater, since the "dirty window" effect is not present with motion compensation. It is important to perform the motion estimation with fractional pel accuracy. Field coding with a switched predictor using previous field in moving areas is an interesting alternative to frame coding with frame difference prediction. View full abstract»

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  • Adaptive Estimator of a Filter and Its Inverse

    Publication Year: 1985 , Page(s): 1281 - 1284
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (312 KB)  

    This paper describes the LMS adaptive filter which compensates for the effect of a linear filter on a signal. The problem that we had to solve was to compensate a propagation channel with an adaptive filter, which has to be connected in series and in front of the channel. The adaptive filter estimates simultaneously the filter response and its inverse. We show the computer simulations of this system applied to the multipath transmission channel. View full abstract»

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  • On Broadcasting in Radio Networks--Problem Analysis and Protocol Design

    Publication Year: 1985 , Page(s): 1240 - 1246
    Cited by:  Papers (61)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (856 KB)  

    In this paper we develop a graph-oriented model for dealing with broadcasting in radio networks. Using this model, optimality in broadcasting protocols is defined, and it is shown that the problem of finding an optimal protocol is NP-hard. A polynomial time algorithm is proposed under which a channel is assigned to nodes from global, multiple-source broadcasting considerations. In particular, nodes participating in the broadcast do not interfere with each other's transmissions, but otherwise simultaneous channel reuse is permitted. Protocol implementations of this approach by frequency division and by time division are given. It is shown that, using these protocols, bounded delay for broadcasted messages can be guaranteed. 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