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Communications, IEEE Transactions on

Issue 3  Part 2 • Date June 1972

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Displaying Results 1 - 25 of 65
  • [Front cover and table of contents]

    Publication Year: 1972 , Page(s): 0
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  • Editorial

    Publication Year: 1972 , Page(s): 263
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  • Comments on "The Divergence and Bhattacharyya Distance Measures in Signal Selection"

    Publication Year: 1972 , Page(s): 485
    Cited by:  Papers (11)
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  • Correction to "Random FM in Mobile Radio With Diversity"

    Publication Year: 1972 , Page(s): 487
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  • Correction to "Piecewise Fourier Transformation for Picture Bandwidth Compression"

    Publication Year: 1972 , Page(s): 488 - 492
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  • Correction to "A Survery of Coding Schemes for Transmission or Recording of Digital Data"

    Publication Year: 1972 , Page(s): 492
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  • Issues in Computer Communications

    Publication Year: 1972 , Page(s): 495 - 498
    Cited by:  Papers (1)
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  • [Back cover]

    Publication Year: 1972 , Page(s): 0
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  • Equivalance of Time-Multiplexed and Frequency-Multiplexed Signals in Digital Communications

    Publication Year: 1972 , Page(s): 435 - 438
    Cited by:  Papers (1)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (440 KB)  

    In comparing different techniques for multiplexing N binary data signals into a single channel, time-division multiplexing (TDM) is known to have a theoretic efficiency of 100 percent (neglecting sync power) and thus seems to outperform frequencydivision multiplexing systems (FDM). By considering more general FDM systems, we will show that both TDM and FDM are equivalent and have an efficiency of 100 percent. The difference between the systems is in the multiplexing and demultiplexing subsystems, but not in the performance or in the generated waveforms. View full abstract»

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  • Performance Measures for Transform Data Coding

    Publication Year: 1972 , Page(s): 411 - 415
    Cited by:  Papers (17)
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    This paper develops performance criteria for evaluating transform data coding schemes under computational constraints. Computational constraints that conform with the proposed basis-restricted model give rise to suboptimal coding efficiency characterized by a rate-distortion relation R(D) similar in form to the theoretical rate-distortion function. Numerical examples of this performance measure are presented for Fourier, Walsh, Haar, and Karhunen-Loève transforms. View full abstract»

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  • Noise Analysis for Laser Doppler Velocimeter Systems

    Publication Year: 1972 , Page(s): 296 - 307
    Cited by:  Papers (1)
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    Laser Doppler velocimeters provide a noncontact method for the measurement of velocities. These measurements are, in general, corrupted by noise arising in the transmission and reception of the optical carrier. An analysis is presented for the effect of noise on the output of the velocimeter system under conditions of high scattering center concentrations and Steady flows. Principally, the so-called Gaussian beam optical setup is considered where the intensity distribution of the intersecting laser beams at the observation volume (fringe pattern) is Gaussian. Output noise spectral densities, noise power, and signal-signal-to-noise ratios are derived in terms of the input signal (Doppler carrier)-tonoise ratios and bandwidths of the processing systems. Also, threshold levels for input signal-to-noise ratios are determined and the photodetector performance analyzed. Finally, analogies are drawn where the current analysis is applicable to other areas of communication. View full abstract»

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  • Zero-Crossing Properties of Angle-Modulated Signals

    Publication Year: 1972 , Page(s): 307 - 315
    Cited by:  Papers (14)
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    Most engineers accept that an angle-modulated signal can be demodulated given only its zero crossings. Unfortunately, proofs of this fact tend to be either quite complicated and devoid of physical insight or to incorporate a significant amount of intuition. The treatment in this paper is cast in terms of sampling theory and trigonometric interpolation. Under this viewpoint, the effects of devices such as digital frequency dividers and pulse-count discriminators are quite easy to understand, and the enhanced noise immunity associated with bandwidth expansion can be interpreted in terms of diversity reception. View full abstract»

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  • On the Selection of a Sampling Filter Bandwidth for a Digital Data Detector

    Publication Year: 1972 , Page(s): 438 - 441
    Cited by:  Papers (1)
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    We consider here the problem of selecting the lowpass sampling bandwidth for a digital mechanization of a matchedfilter bit-synchronizer combination. In particular, if digital data at a rate R bits/second plus Gaussian noise is passed through a filter of bandwidth KR and then sampled at the Nyquist rate, i.e., 2 KR , then how small can we choose K without paying an appreciable penalty in the SNR performance of the data detector? View full abstract»

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  • Adaptive Detection With Intersymbol-Interference Cancellation for Distorted Digital Signals

    Publication Year: 1972 , Page(s): 350 - 361
    Cited by:  Papers (4)  |  Patents (1)
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    A theoretical analysis is presented of an adaptive detector in a synchronous serial data-transmission system. A binary-coded signal is transmitted over a baseband channel, which introduces slowly time-varying signal distortion. The received signal is sampled and each signal element is detected by means of an iterative process that uses some or all sample values dependent on that element. The intersymbol interference of the signal element in the following elements is then canceled, before the detection of the next element, and so on. Immediately after the detection of each signal element, the channel impulse response is estimated and the detector is adjusted appropriately, so that it follows the variations in the channel transmission characteristics. No training signal is required except at the start of transmission. The tolerance to additive white Gaussian noise is evaluated for different arrangements of the basic system and for various values of the signal distortion in transmission, assuming the detector to be correctly matched to the channel. View full abstract»

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  • Root-Mean-Square Error in Encoded Digital Telemetry

    Publication Year: 1972 , Page(s): 315 - 320
    Cited by:  Papers (1)
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    This paper studies the effectiveness of certain group codes in reducing the root-mean-square (rms) error in a digital telemetry link. The zero-sampling-error lower bound on the total error is derived for the case when majority-logic-decodable group codes are used in the channel. Calculated data are presented for several such codes including two new cyclic unequal-error-protection codes. View full abstract»

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  • Evaluation of Optimal Routing Policies in Communication Nets by Simulation

    Publication Year: 1972 , Page(s): 264 - 274
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    A Monte Carlo simulation program that enables the evaluation of different routing policies in a communication network is described. This simulation is intended to deal with nonoriented (telephone) networks and the grade of service (G/S) is taken as the performance measure. However, it can easily be adapted to deal with oriented or mixed networks. The program assigns to each branch of the analyzed network a price function. For each call, the route of minimal cost, among all available under the present load conditions in the network, is then chosen. The program was used for comparing routing policies, as initiated by different price functions. The comparisons were made on several test networks and for different traffic loads. The results obtained showed a significant improvement in the G/S for the policy that aimed at distributing the flow through the network in the most homogenous way possible. This homogenous flow distribution was obtained by using the above minimal-cost policy and a price function, assigned to each channel, that monotonically increases with the traffic load of the branch to which the particular channel belongs. The influence of the topological configuration of the network on the G/S, under equal external demands, was also investigated and the results are given. The way in which the results are printed out enables the simulation program to serve also as a practical and useful tool in the design (or the redesign) of a communication net. View full abstract»

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  • Longitudinal Balance Measurement of Central Office Equipment

    Publication Year: 1972 , Page(s): 382 - 391
    Cited by:  Patents (1)
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    Longitudinal balance should be measured by a standard method that will accurately show the degree of unbalance to ground of components or networks. The method proposed by the IEEE's Wire Communication Committee and under consideration by International Telephone and Telegraph Consultative Committee (CCITT), was tested, using techniques found necessary to avoid errors. Calculated data were used to prove the precision of measurements, and are included to indicate the magnitude of unbalance caused by resistors, capacitors, and inductors. View full abstract»

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  • The Behavior of Dynamic Channel-Assignment Mobile Communications Systems as a Function of Numbers of Radio Channels

    Publication Year: 1972 , Page(s): 471 - 479
    Cited by:  Papers (13)  |  Patents (3)
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    Dynamic channel assignment in mobile communications systems is able to cope with varying nonuniform spatial user demand. It also readily handles the normal randomness in offered traffic. This study presents system performance data for radio systems having 8, 20, 40, 80, and 120 radio channels available and a radio-channel reuse interval of 4 base-station coverage areas. Data are also presented that compare performance of a 30 radiochannel system with a reuse interval of 3 base stations, a 40 radiochannel system with a reuse interval of 4 base stations, and a 50 radio-channel system with a reuse interval of 5 base stations. The results are obtained from a computer simulation of a onedimensional network laid out along a line. As the number of radio channels available to a communication system increases, the system becomes more efficient in handling the fluctuations in offered traffic. Changing the radio-channel reuse interval also affects the per-channel traffic carried by a dynamic-channel-assignment system. View full abstract»

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  • The Performance of Fading Frequency-Shift-Keyed Telemetry Systems with Bandpass Limiters

    Publication Year: 1972 , Page(s): 403 - 406
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    In this paper the performance of a radiometric receiver preceded by a bandpass limiter is studied when the input is a fading binary frequency-shift-keyed signal. An expression for the probability of error versus signal-to-noise ratio, with receiver bandwidth as a parameter is derived. It is seen that limiting does not necessarily improve receiver performance, as is often thought. View full abstract»

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  • Audio Tone Relaying Tests on Telephone Channels in the Presence of Induced Voltage

    Publication Year: 1972 , Page(s): 392 - 399
    Cited by:  Papers (4)
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    Wire-line channels are often used for transmission of high-speed protective relaying signals at power stations. In situations where the communications plant is exposed to severe environmental stress during a power fault, special engineering of plant protection is necessary. A series of staged faults in an inductive environment was conducted jointly by the Bell System and Public Service of Colorado. The purpose of these tests was to observe the operation of the relaying terminals and monitor the communication system during a fault. A series of steps was taken to ensure cable dielectric integrity and eliminate sources of transmission interference. The communications system was stressed with up to 3800 V. rms generated by electromagnetic induction from a parallel faulted ll5-kV power line. The resulting specially engineered communications system withstood the induced voltage and allowed reliable transmission of relaying signals. View full abstract»

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  • High-Capacity Microwave System for Digital Data Transmission

    Publication Year: 1972 , Page(s): 466 - 470
    Cited by:  Papers (17)
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    A nationwide data network is planned that will employ microwave relay networks for both long-haul and short-haul interconnection. A digital modulation technique has been developed that has the constant level advantage of frequency-shift keying (FSK) systems while retaining the error rate and threshold performance of coherently detected binary or four-phase phase-shift keying (PSK). Occupied spectrum and interference characteristics of a 21.5-Mbit/s data system are compared to the more conventional 600-, 1200-, and 1800-channel message systems. View full abstract»

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  • The Digital Phase-Locked Loop as a Near-Optimum FM Demodulator

    Publication Year: 1972 , Page(s): 406 - 411
    Cited by:  Papers (22)
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    This paper presents an approach to the optimum digital demodulation of a continuous-time FM signal using stochastic estimation theory. The primary result is a digital phase-locked loop realization possessing performance characteristics that approach those of the analog counterpart. Some practical considerations are presented and simulation results for a first-order message model are presented. View full abstract»

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  • Subjective Effects of Channel Transmission Errors on PCM and DPCM Voice Communication Systems

    Publication Year: 1972 , Page(s): 281 - 290
    Cited by:  Papers (5)
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    Isopreference tests were used to study the subjective effects of channel transmission errors on computer-simulated PCM and previous-sample feedback DPCM voice systems. Numerically scaled isopreference contours were obtained and plotted on planes having as axes the number of quantization bits N and the bit error probability p of the binary symmetric transmission channel. For any N and p considered, the quality of DPCM speech was found to exceed that of PCM speech. With N fixed and p decreasing, the improvement of DPCM relative to PCM increased to the point where quantization noise limited the performance of both systems. Two nonredundant codes, natural binary and folded binary, were used to encode the quantizer output. The two codes yielded comparable speech quality. The maximum subjective quality obtainable for white Gaussian and Rayleigh fading channels was determined as a function of channel capacity. Use of optimum channel encoding was shown to reduce considerably the channel capacity required to obtain a given speech quality. The subjective ratings were compared with measured system signal-to-noise ratios. Finally, the effect of the overload level of the quantizer on the system signal-to-noise ratio was determined. View full abstract»

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  • On the Analysis and Modeling of a Class of Computer Communication Systems

    Publication Year: 1972 , Page(s): 645 - 660
    Cited by:  Papers (41)
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    Recent advances in computer communications are discussed including computer-traffic and channel error characteristics, optimal fixed message block size, statistical multiplexing, and loop systems. A unified model is developed and then used to analyze the queueing behavior of the star and loop systems. Numerical results for selected traffic intensities and message lengths, given in graphical form, provide insight into the performance of these systems. View full abstract»

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  • Optimizing the Reliability in Centralized Computer Networks

    Publication Year: 1972 , Page(s): 640 - 644
    Cited by:  Papers (7)
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    This paper deals with a heuristic procedure for optimizing the reliability of computer networks consisting of clusters of terminals connected to remote concentrators that are connected to a data-processing center. The expected percentage of terminals connected to the processing center is used as a measure of network reliability. It is shown that configurations other than the frequently used star are often considerably more reliable and less expensive. 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.

 

 

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Robert Schober
University of British Columbia