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Communications, IEEE Transactions on

Issue 3 • Date March 1979

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Displaying Results 1 - 21 of 21
  • [Front cover and table of contents]

    Publication Year: 1979 , Page(s): 0
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    Freely Available from IEEE
  • [Back cover]

    Publication Year: 1979 , Page(s): 0
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    Freely Available from IEEE
  • Design and Implementation of a Signaling Handling Unit for Electronic Exchanges

    Publication Year: 1979 , Page(s): 591 - 596
    Cited by:  Papers (1)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (616 KB)  

    Design of a unit which handles functions of line scanning, digit forming, and digit pulsing fully independent of the main processor has been presented. These functions as implemented in conventional systems form a major portion of the real time load on the processor. The hardware unit described in this paper takes care of all these functions with only nominal interaction with the processsor, thereby reducing considerably the real time load. In this unit one very high speed logic assembly is shared by a large number of lines with the help of memory and timing circuits. The same hardware with only minor modifications can be used for telex application also. A typical unit for 1000 lines requires about 300 IC's. This includes the processor interface. View full abstract»

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  • Addendum to "Volterra Systems with Random Inputs: A Formalized Approach"

    Publication Year: 1979 , Page(s): 636 - 638
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    A newly derived expression for the higher order crosscorrelation function of two jointly stationary Gaussian random processes is used to determine the output autocorrelation function of a Volterra system driven by a Gaussian input and to simplify a previously published expression for the output power spectral density and its derivation. View full abstract»

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  • Improved Phase-Locked Loop Performance Via Nonlinear Loop Filters

    Publication Year: 1979 , Page(s): 542 - 556
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1072 KB)  

    A new structure for the loop filter of a PLL which consists of a conventional linear first order filter connected in a feedback arrangement with a static nonlinearity is analyzed. In the absence of noise, the steady state operating conditions (i.e., equilibrium points) are independent of the parameters of the nonlinearity, and asymptotic stability of the PLL for sufficiently small frequency detuning is established independent of the initial conditions of the VCO. Due to the nonlinearity, the resulting performance of the PLL during the acquisition node is greatly improved with little resulting loss in the narrowband filtering capability of the loop. Using Volterra methods, an explicit expression for the variance of the phase error for a cubic nonlinearity is developed which compares favorably with simulation studies. View full abstract»

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  • ALOHA/TDM Systems with Multiple Downlink Capacity

    Publication Year: 1979 , Page(s): 537 - 541
    Cited by:  Papers (10)
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    The concept of a processing satellite with multiple slotted ALOHA uplinks to efficiently fill a TDM downlink is extended to include multiple downlinks. Throughput is derived for a general configuration with n ALOHA uplinks and m TDM downlinks. An optimization procedure is described to select the n and m which maximize throughput for a given bandwidth constraint. The ALOHA/TDM system with multiple downlink capacity is found to be up to 32% more spectrum-efficient than the conventional slotted ALOHA system. The ALOHA/TDM system also has the potential for payload power and weight savings and decreased passive intermodulation problems. View full abstract»

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  • Linearization of Multichannel Analog Optical Transmitters by Quasi-Feedforward Compensation Technique

    Publication Year: 1979 , Page(s): 582 - 588
    Cited by:  Papers (9)  |  Patents (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (784 KB)  

    A quasi-feedforward compensation technique is described for linearization of LED's in analog fiber optics based video transmission systems, Experimentally we have observed an improvement of more than 35 dB in second-order and 20 dB in third-order distortion in a system transmitting three TV channels simultaneously. The linearized system is capable of video signal transmission over a distance of at least 2 km without repeaters. View full abstract»

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  • The Single Server Queue with Periodic Arrival Process and Deterministic Service Times

    Publication Year: 1979 , Page(s): 556 - 562
    Cited by:  Papers (44)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (544 KB)  

    We derive an algorithm for computing the exact delay distribution for the following first-come-first-served single server queue. The arrival process is the superposition of N + 1 independent equivalent deterministic arrival streams, and the service times are deterministic. Numerical results are used to compare this system with an approximating system which has been used in the absence of exact results: the M/D/1 queue (Poisson input, deterministic service time). A comparison with a finite source model is also given. This study was motivated by the following issue germane to packet switching data networks. There are N + 1 packet processes, arriving over identical trunks, which must share the transmission capacity of a single high-speed trunk in a store-and-forward manner. The idealized queueing model above analyzes the worst-delay situation for this problem when the incoming trunks are fully utilized and the packets are maximum sized. The results indicate that an M/D/1 approximation can be quite pessimistic in predicting the performance of such a system. View full abstract»

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  • Binary CPSK Performance Analysis for Saturating Band-Limited Channels

    Publication Year: 1979 , Page(s): 596 - 603
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (640 KB)  

    An expression is derived for the error probability of binary CPSK signals received over a soft-limited channel in the presence of pre- and post-limiter additive Ganssian noise. Although this expression is not in closed form, it may be efficiently evaluated to any desired accuracy using a recurrence method developed in the appendix. System performance is also evaluated when the signals are subjected to bandlimiting as well as Gaussian noise preceding the limiter. Moment space techniques are used to obtain upper and lower bounds on the errorrate in terms of the error-rate in the presence of Gaussian noise alone. Numerical examples are presented for a channel which includes a Chebyshev filter preceding the limiter. These illustrate that the bounds are tight enough for most practical purposes. View full abstract»

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  • Experimental Investigation of Some Effects of Multipath Propagation on a Line-of-Sight Path at 14 GHz

    Publication Year: 1979 , Page(s): 643 - 647
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (488 KB)  

    A microwave line-of-sight propagation experiment is carried out in Denmark at frequencies around 14 GHz. Results from long term measurements of multipath propagation are presented. The multipath fade durations are shown to be log-normally distributed. The level dependence of the probability of fading, P , the average duration of fades, \bar{t} , and the number of fades, N0, is investigated. Results show that P \propto L^{2} , \bar{t} \propto L^{2/3} and N_{0} \propto L^{4/3} . This differs from previously published results, where proportionalities of L2, L and L , respectively, have been proposed. Statistical results on enhancements above free space level are also presented. The results presented are believed to enable an improved description of the effects of multipath propagation. View full abstract»

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  • Logistic Function to Describe the Legibility of Transmitted Alphanumerics

    Publication Year: 1979 , Page(s): 619 - 623
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (600 KB)  

    A mathematical model, based on the logistic function, is proposed to describe the legibility of alphanumerics transmitted by facsimile or by television. The model has been successfully applied to results obtained with examples of both types of systems. It describes the effects of both horizontal and vertical definition, at the same time reflecting the additive effect of one parameter on the other. View full abstract»

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  • Simple Approximations of the Error Function Q(x) for Communications Applications

    Publication Year: 1979 , Page(s): 639 - 643
    Cited by:  Papers (64)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (392 KB)  

    Simple analytical upper bounds, approximations and lower bounds on the error function Q(x) are presented and analyzed. A class of functions are given, where the choice of two parameters result in good upper bounds, lower bounds and approximations on Q(x) . The results are given in formulas, parameter tables and graphs. The approximations are suitable for programmable pocket calculators. View full abstract»

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  • An Almost Linear Relation Between the Step Size Behavior and the Input Signal Intensity in Robust Adaptive Quantization

    Publication Year: 1979 , Page(s): 623 - 629
    Cited by:  Papers (5)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (648 KB)  

    A considerable amount of information regarding the behavior and performance of robust adaptive quantizers is contained in the function C(\sigma ) which denotes the dependence of the central (or typical) step size, C , on the intensity, σ, of the input random variables. The graphical representation of C(\sigma ) is called the load curve. It is quite remarkable that plots of log C(\sigma ) are found to be almost linearly dependent on log σ. One of our contributions is to show that this linearity follows from an unusual, but quite effective, approximation to the Gaussian and Laplacian distributions of the input random variables. The central result is a quite explicit expression for the function C(\sigma ) , and thus for the load curve, derived from the aforementioned approximation: \log C(\sigma ) = S \log \sigma + T . The quantities S and T are explicitly given in terms of the various fixed parameters of the system. The expression for S provides insight into the tradeoffs between the dynamic range of the step size, the robustness in the presence of channel errors and the ability to track changes in the signal intensity σ. View full abstract»

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  • The Influence of Protocols on the Stability Conditions in Packet-Switching Networks

    Publication Year: 1979 , Page(s): 611 - 619
    Cited by:  Papers (5)
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    A packet-switching network is considered as a tandem system of store-and-forward links. In this paper, it is shown that the maximum input traffic, with finite intermediate buffer size, is very sensitive to the distribution of the transmission time. The performance of two different protocols is compared under various distributions of transmission times. View full abstract»

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  • Power Division in Spread Spectrum Systems with Limiting

    Publication Year: 1979 , Page(s): 574 - 582
    Cited by:  Papers (7)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (712 KB)  

    This paper finds power division through a bandpass nonlinearity when the input is two spread spectrum signals plus noise. This model applies to code division multiple access (CDMA) satellites or to multiple transmission of CDMA through a common Earth terminal transmitter. The solution requires finding a single attenuation constant for each input signal including the input noise. This approach provides the first exact power division solutions for spectrally overlapping, possibly coherently generated, spread spectrum signals plus noise through a bandpass limiter. Two examples illustrate the approach. Simultaneous transmission of coherently generated QPSK spread signals through a hard limiter without noise may cause whichever is the smaller of the two to suffer a sharp 6 dB suppression. This suppression is highly phase dependent and can be alleviated by proper phasing of the signals prior to hard limiting. In the second example, input/output SNR relations are found and compared with those given by Jones for two unmodulated sine waves and noise. A significant reduction in output SNR exists for spread signals compared to the two sine wave case examined by Jones. View full abstract»

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  • Optimal Packet Length for Packet Voice Communication

    Publication Year: 1979 , Page(s): 607 - 611
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (448 KB)  

    It is shown that for typical operating parameters, the optimal packet length for a single link packet voice system is of the order of 300-700 bits. This is contrary to both the optimal length of a data packet (approximately 1000 bits), and documented experimental implementations of such network architecture for voice (approximately 1000 bits). View full abstract»

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  • Call Repacking in Connecting Networks

    Publication Year: 1979 , Page(s): 589 - 591
    Cited by:  Papers (22)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (320 KB)  

    A method for increasing the traffic capacity of connecting networks is presented which involves rearrangement of calls while in progress. In contrast to previously studied methods for rearrangement of existing calls, the process involves repacking calls as existing calls terminate, rather than when arriving calls are blocked. The scheme has the advantage that the added control complexity is much less than required for rearrangement in the normal sense. View full abstract»

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  • Two Discrete-Time Queues in Tandem

    Publication Year: 1979 , Page(s): 563 - 573
    Cited by:  Papers (23)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (720 KB)  

    A discrete-time queueing problem involving two queues in tandem, with unit service time, is considered. Such a situation can arise within a packet-switching network. Arrivals at the queues occur from separate sources, which may be correlated. The joint arrivals from the two sources are assumed to be independently and identically distributed in each unit time interval. In addition, the output of the first queue enters the second queue. Both queues are assumed to have unlimited size, and the generating function of the steady state distribution of the two queue lengths is calculated, under the assumption that the mean combined input rate from the two sources is less than unity. The average waiting times are also derived, under the assumption that all arrivals take place at the end of a unit time interval. A particular example, in which the input to the first queue is geometrically distributed in each unit time interval, while the input from the source into the second queue is either 0 or 1, with fixed probabilities, is analyzed. The steady state probability that the length of the second queue exceeds m is calculated. The asymptotic behavior for m \gg 1 changes significantly when a certain threshold, depending on the mean input rates, is reached. Numerical results are presented. View full abstract»

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  • Subscriber-Loop Digital Transmission Using Opto-Electronic Transmitters and Receivers

    Publication Year: 1979 , Page(s): 629 - 635
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (536 KB)  

    The efficiencies of different methods for subscriber-loop digital transmission are compared, using as a criterion the cost per bit/second per kilometer of wire, denoted "CSP". Approaches to reduction of CSP are suggested, in particular the use of opto-electronic transmitters and receivers in a differential connection, resulting in a relatively noise-immune subscriber line. A graphic method for the analysis of opto-electronic digital transmission lines is described. View full abstract»

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  • Analytic Approximation of Blocking Probabilities in Circuit Switched Communication Networks

    Publication Year: 1979 , Page(s): 603 - 606
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (416 KB)  

    A method inspired from S. Katz's service evaluation algorithm [6] is presented. The new algorithm is recursive, rather than iterative, in nature, and especially suited for networks that do not contain cycles. It also introduces two new features which take existing theoretical results into account, and as such corresponds more closely to the current state of traffic theory. View full abstract»

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  • Assigning a Minimal Multiple-Center Under a Given Reliability Index in Tree Networks

    Publication Year: 1979 , Page(s): 638 - 639
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    An efficient algorithm is presented for assigning a minimal multiple-center in a tree network that satisfies a given reliability index. 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