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Communications, IEEE Transactions on

Issue 7 • Date July 1985

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Displaying Results 1 - 25 of 28
  • [Front cover and table of contents]

    Publication Year: 1985 , Page(s): 0
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    Freely Available from IEEE
  • Corrections to "Mathematical Models for Cochannel Interference in FH/MFSK Multiple Access Systems"

    Publication Year: 1985 , Page(s): 721
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (139 KB)  

    First Page of the Article
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  • [Back cover]

    Publication Year: 1985 , Page(s): 0
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    Freely Available from IEEE
  • Performance Assessment of Band-Limited Limiting and Blanking Communication Systems

    Publication Year: 1985 , Page(s): 711 - 715
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (472 KB)  

    This paper presents a general formulation of piecewise linear (PWL) models of voltage transfer functions to characterize channel nonlinearities in satellite digital communication systems. This formulation provides a tractable approach to evaluate the performance of such systems with band-limited PWL limiters, channel blanking, and hardlimiters. The envelope characteristics of the PWL models are derived in terms of breakpoints and slopes of PWL segments. Intermodulation (IM) products, their statistical properties, and the resultant error probability performance of such BPSK systems, subject to CW interference, are numerically illustrated through these PWL models. View full abstract»

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  • Performance of Baseband Digital Data Transmission in Nonlinear Channels with Memory

    Publication Year: 1985 , Page(s): 715 - 719
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (408 KB)  

    This paper considers the performance of digital data transmission in nonlinear channels with memory. The analysis is based on the application of a particular form of Volterra series representation for the nonlinear system describing the transmission channel. First, expressions are derived for the output mean and power spectral density under certain conditions. Next, the paper presents a computationally convenient expression for the error rate involved in such transmission. View full abstract»

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  • Performance Analysis of Tandem Burst-Error Links with Applications to ISDN

    Publication Year: 1985 , Page(s): 646 - 653
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (648 KB)  

    In this paper, tandem links with burst errors are analyzed using the Gilbert model for individual links. The results, apart from being of general interest, are of particular relevance to the Integrated Services Digital Networks (ISDN) for which the International Telegraph and Telephone Consultative Committee (CCITT) is currently developing performance specifications based on hypothetical reference connections (HRX's), i.e., composite channels consisting of several tandem reference circuits. The average error rate, the error gap distribution, its mean, and a tight upper bound on its standard deviation are analytically derived for the composite channel (equivalent to an HRX) with N tandem links (circuits). These statistics are then related to the performance measures proposed for ISDN. Some numerical results are presented to highlight the large differences in the estimated performance with a burst-error model approach and with an independent-error approach (having identical average error probabilities). View full abstract»

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  • Collision Resolution Protocols Utilizing Absorptions and Collision Multiplicities

    Publication Year: 1985 , Page(s): 721 - 724
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    In this correspondence, we consider the random accessing of a single slotted channel by a large number of packet transmitting users, whose cumulative traffic is Poisson. We assume the existence of the same feedback as that of the MCRAI protocols of Georgiadis, and full channel sensing, and we develop collision resolution algorithms that utilize the absorption concept of Gallager. We observe the improvement in the throughputs induced by the absorption, as well as the improved delay characteristics. Finally, we draw some conclusions about the limitations of the absorption idea. View full abstract»

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  • A Note Upon Another Error Detecting Code That Is Not Proper

    Publication Year: 1985 , Page(s): 719 - 721
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (336 KB)  

    In this correspondence, the performance of the nonlinear error-detecting code, described in CCIR Recommendation 476-2, when used over a memoryless binary symmetric channel (BSC), is derived. From this, it is apparent that the probability of accepting an erroneous block is not a monotonic function of the bit error probability, but rather reaches a peak of 5.653 percent when the bit error probability is 11.66 percent. Consequently, this code is not proper [1]-[6]. View full abstract»

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  • Data-Sequence Selective Timing Recovery for PAM Systems

    Publication Year: 1985 , Page(s): 729 - 731
    Cited by:  Papers (9)  |  Patents (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (312 KB)  

    An adaptive baud-rate timing recovery scheme for digital communications, suitable for implementation using digital signal processing techniques, is described. Its principal advantages are that determination of functions yielding timing error estimates is simple, and that these estimates are low-variance. This is achieved by calculating timing error estimates only when certain suitable data sequences occur. View full abstract»

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  • Differential Detection of Narrow-Band Binary FM

    Publication Year: 1985 , Page(s): 725 - 729
    Cited by:  Papers (8)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (432 KB)  

    In this paper we consider differential detection of narrowband binary FM, using a detector which utilizes a delay line whose delay period is dependent on the value of the modulation index. The error-rate performance is computed for this receiver and compared with that of the limiter-discriminator receiver. In contrast to the previously published results for one-bit delay differential detection, it is shown that variable delay differential detection yields performance comparable to limiterdiscriminator detection. View full abstract»

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  • A Further Investigation of Max's Algorithm for Optimum Quantization

    Publication Year: 1985 , Page(s): 746 - 750
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (456 KB)  

    Although Max's algorithm is frequently thought of as a simple and adequate method for the design of scalar minimum mean squared error quantizers, there are two tactical problems associated with this iterative scheme: the initialization and the updating of the algorithm. This paper proposes easy and efficient solutions to these problems. A straightforward method for obtaining good initial conditions for three common input densities is presented. Also, an efficient technique for updating the algorithm for a wide class of input densities is given. View full abstract»

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  • The Optimal Retry Distribution for Lightly Loaded Slotted Aloha Systems

    Publication Year: 1985 , Page(s): 724 - 725
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    Most of the analytical work on slotted Aloha has been concerned with maximizing the utilization. The delay experienced by a transmission has not been a primary issue. In this note we take the opposite point of view. It is assumed that the system is operating far below capacity (as is typical in practice), and we concern ourselves with the problem of minimizing packet delay in the event of a collision. The retry distribution that minimizes the average delay is derived. Surprisingly, the optimal retry distribution has finite support, and in fact, one never waits more than three slots before retransmitting. View full abstract»

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  • Envelope Detection of Binary VSB Data Signals

    Publication Year: 1985 , Page(s): 732 - 735
    Cited by:  Papers (1)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (432 KB)  

    The performance of vestigial-sideband data transmission systems employing envelope detection is considered in the context of broad-band local area networks (BLAN's). General results for horizontal and vertical eye opening are presented and noise performance is assessed for three systems of particular interest. It is concluded that this data transmission scheme is suitable for BLAN's. View full abstract»

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  • Decision Feedback Equalization of Dispersive Radio Channels

    Publication Year: 1985 , Page(s): 676 - 684
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (840 KB)  

    The performance of adaptive decision feedback equalization applied to high bit rate digital radio systems in the presence of multipath propagation is analytically investigated. Minimum phase (MP) and nonminimum phase (NMP) type fades as well as the transition periods between these two states are considered. Insight is given into the IF recovered timing epoch and its consequences on the decision feedback equalizer (DFE) behavior, especially during transition periods. Required conditions on the DFE structure for ensuring its maximum efficiency are derived and a modified updating algorithm is presented. Finally, dynamic simulation results are reported and compared to theoretical results. They show that the proposed structure is capable of coping with most propagation conditions. View full abstract»

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  • Noise Performance and SNR Threshold in PFM

    Publication Year: 1985 , Page(s): 708 - 711
    Cited by:  Papers (1)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (440 KB)  

    Pulse frequency modulation (PFM) has been considered by several authors for transmitting wide-band signals. However, the noise performance of PFM has been analyzed only above the SNR threshold. In this correspondence the results on the noise performance of PFM available in the literature are summarized, and a more general expression describing noise performance of PFM, both above and below the SNR threshold, is derived. This expression can be used to evaluate the SNR threshold for channels with both signal-independent noise (e.g., metallic facilities) and signal-dependent noise (e.g., fiber optic facilities). In particular, it is shown that in systems with signal-independent white noise, the SNR threshold is approximately 20 dB. View full abstract»

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  • Analysis and Simulation of a Digital Mobile Channel Using Orthogonal Frequency Division Multiplexing

    Publication Year: 1985 , Page(s): 665 - 675
    Cited by:  Papers (878)  |  Patents (244)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1080 KB)  

    This paper discusses the analysis and simulation of a technique for combating the effects of multipath propagation and cochannel interference on a narrow-band digital mobile channel. This system uses the discrete Fourier transform to orthogonally frequency multiplex many narrow subchannels, each signaling at a very low rate, into one high-rate channel. When this technique is used with pilot-based correction, the effects of flat Rayleigh fading can be reduced significantly. An improvement in signal-to-interference ratio of 6 dB can be obtained over the bursty Rayleigh channel. In addition, with each subchannel signaling at a low rate, this technique can provide added protection against delay spread. To enhance the behavior of the technique in a heavily frequency-selective environment, interpolated pilots are used. A frequency offset reference scheme is employed for the pilots to improve protection against cochannel interference. View full abstract»

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  • Encoding of Arbitrary Curves Based on the Chain Code Representation

    Publication Year: 1985 , Page(s): 697 - 707
    Cited by:  Papers (43)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (992 KB)  

    An efficient encoding scheme for arbitrary curves, based on the chain code representation, has been proposed. The encoding scheme takes advantage of the property that a curve with gentle curvature is divided into somewhat long curve sections (segments), each of which is represented by a sequence of two adjacent-direction chain codes. The coding efficiency of the scheme becomes higher as the segments become longer, while a variable-length coding technique makes it possible to encode short segments without an extreme increase in code amount. An experiment with complicated curves obtained from geographic maps has shown a high data compression rate of the proposed scheme, whose code amount is about 50-60 percent of that required for the conventional chain encoding scheme. View full abstract»

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  • An Efficient RLS Data-Driven Echo Canceller for Fast Initialization of Full-Duplex Data Transmission

    Publication Year: 1985 , Page(s): 601 - 611
    Cited by:  Papers (16)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1200 KB)  

    Computationally efficient recursive-least-squares (RLS) procedures are presented specifically for the adaptive adjustment of the data-driven echo cancellers (DDEC's) that are used in voiceband fullduplex data transmission. The methods are shown to yield very short learning times for the DDEC, while they also simultaneously reduce computational requirements to below those required for other leastsquare procedures, such as those recently proposed by Salz (1983). The new methods can be used with any training sequence over any number of iterations, unlike any of the previous fast-Converging methods. The methods are based upon the fast transversal filter (FTF) RLS adaptive filtering algorithms that were independently introduced by the authors of this paper; however, several special features of the DDEC are introduced and exploited to further reduce computation to the levels that would be required for slower-converging stochastic-gradient solutions. Several tradeoffs between computation, memory, learning time, and performance are also illuminated for the new initialization methods. View full abstract»

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  • L-Expressnet: The Communication Subnetwork for the C-NET Project

    Publication Year: 1985 , Page(s): 612 - 619
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (904 KB)  

    L-Expressnet is the communication suxbnetwork for the CNET local area network project of the CNR, Italy. Based on a single bus topology, it utilizes a simple and efficient virtual-token access protocol which provides ordered and collision-free transmission. The paper discusses the needs which led to L-Expressnet, describes the protocol, proves its correct operation, and compares its throughput-delay performance with those of other typical bus Protocols. A major advantage of L-Expressnet is that its implementation may be based on Ethernet standard transceivers and network interfaces. View full abstract»

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  • Throughput Analysis for Persistent CSMA Systems

    Publication Year: 1985 , Page(s): 627 - 638
    Cited by:  Papers (61)  |  Patents (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (920 KB)  

    The channel throughput for a finite number of packet broadcasting users is analyzed for random access protocols, including slotted persistent carrier sense multiple access (CSMA) with and without collision detection and unslotted persistent CSMA with and without collision detection. We consider both p - and 1-persistent CSMA. Our results can be extended to infinite population cases (by taking the proper limit), where they agree with the known throughput expressions when available. View full abstract»

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  • On the Performance of Speech Waveform Coders with Noise Spectral Shaping

    Publication Year: 1985 , Page(s): 742 - 746
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (544 KB)  

    The performance of speech waveform coders that incorporate a noise spectral shaping filter is discussed. The coders studied are adaptive pulse code modulation (APCM), adaptive differential PCM (ADPCM), and adaptive delta modulation (ADM). For APCM and ADPCM, the noise shaping filter is designed to minimize the C-message weighted quantization noise power. As for ADM, the noise shaping filter is used to move some portion of in-band noise outside the signal band. Simulation results show that the performance improvement of these waveform coders with spectral shaping is about 0.5-3 dB over the systems without noise shaping. Although this improvement is relatively small, the waveform coders with noise spectral shaping yield subjectively more pleasing and intelligible sound than those without it. View full abstract»

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  • Analysis of Jitter Peaking Effects in Digital Long-Haul Transmission Systems Using SAW-Filter Retiming

    Publication Year: 1985 , Page(s): 654 - 664
    Cited by:  Papers (10)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1112 KB)  

    The new lightwave long-haul transmission systems typically use surface-acoustic-wave (SAW) filters for timing recovery, in place of the phase-locked loops favored in slower systems. We report here analytical studies of jitter phenomena allowed by two kinds of filter ripple. The ripple is capable of causing jitter to accumulate exponentially with the number of regenerators N in a repeatered line. Such behavior is well known in the case of phase-locked-loop retiming, where the "jitter peaking" that usually appears in the loop response must be carefully limited to avoid exponential jitter growth. We show that equivalent phenomena can appear when the SAW filters exhibit passband ripple, or, as previously reported in condensed form, When ripple-free filters are detuned by approximately one-half the full 3 dB bandwidth. Furthermore, in the case of ripply filters, exponential jitter accumulation is found to be much more pronounced for random jitter than for systematic jitter. In addition, the alignment jitter within each regenerator can grow exponentially along the chain of regenerators. Neither of these statements is true in the case of the ripple-free filters previously treated in the literature. View full abstract»

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  • Priority Access Schemes Using CSMA-CD

    Publication Year: 1985 , Page(s): 620 - 626
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (752 KB)  

    Some CSMA-CD schemes for multiple priority message classes are suggested. For all the schemes, an approximate analytic technique for calculating the mean packet delay (for each priority) at the stable operating point of the system has been developed. The analytic results are tested against computer simulation. A Poisson packet arrival process and a general packet length distribution are considered. The mean packet retransmission delay is a general function of priority and the number of unsuccessful attempts. There is a variation in delay differences among priorities for the different schemes. This allows one to single out the particular scheme that is optimal for a given system delay requirement. Some of the priority schemes possess the desirable property of having less average delay compared to a corresponding nonpriority system. View full abstract»

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  • Rapid Acquisition for Direct Sequence Spread-Spectrum Communications Using Parallel SAW Convolvers

    Publication Year: 1985 , Page(s): 593 - 600
    Cited by:  Papers (58)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (648 KB)  

    In this paper, a technique is described which uses multiple surface acoustic wave (SAW) devices in parallel to reduce the acquisition time of a direct sequence spread-spectrum communication system. Analysis of system performance in both the search and lock modes is presented, and key quantities such as probability of false alarm, probability of correct detection, mean dwell time, and mean time to lose lock are derived. View full abstract»

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  • Pseudobinary and Pseudoquaternary Detection Processes for Linearly Distorted Multilevel QAM Signals

    Publication Year: 1985 , Page(s): 639 - 645
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (936 KB)  

    The paper describes two new detection processes suitable for QAM signals that have 16 or more levels (possible data symbol values) and that have been subjected to linear distortion, causing severe intersymbol interference in the received signal. The detectors are developments of the pseudobinary systems previously described, and are designed to operate in the presence of severe intersymbol interference. Results of computer simulation tests are presented, comparing the tolerances to additive white Gaussian noise of various arrangements of each detector with those of more conventional detectors. The tests have been carried out on a model of a 19 200 bit/s synchronous serial data transmission system, operating with a 64-level QAM signal that is transmitted, in turn, over two different telephone circuits. 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