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Communications, IEEE Transactions on

Issue 11 • Date November 1983

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Displaying Results 1 - 14 of 14
  • [Front cover and table of contents]

    Publication Year: 1983 , Page(s): 0
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  • Comment on "Analysis of a Mobile Radio Communication System with Two Types of Customers and Priority"

    Publication Year: 1983 , Page(s): 1255 - 1256
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  • Author's reply

    Publication Year: 1983 , Page(s): 1256 - 1257
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  • [Back cover]

    Publication Year: 1983 , Page(s): 0
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  • Transmission of Two NTSC Color Television Signals Over a Single Satellite Transponder Via Time-Frequency Multiplexing

    Publication Year: 1983 , Page(s): 1257 - 1266
    Cited by:  Papers (2)  |  Patents (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1056 KB)  

    We describe a time-frequency multiplexing (TFM) method for transmitting two television signals over one satellite transponder, which gives significant improvement over existing methods. The complexity of the hardware implementation is similar to existing time-division multiplexing (TDM) systems, but the picture quality, when received on a 10 m earth station, approaches that which is currently being requested by the major television networks. Unlike existing frequency-division multiplexing (FDM) systems, TFM needs no backoff of the satellite transponder. The general philosophy of TFM is described, including the benefits of using a difference signal to reduce the overall required bandwidth. Also discussed is companding of the difference signal as a means of improving the overall signal-to-noise ratio. Several alternative methods of implementation are considered, along with those which have been explored in some detail. We then describe an experimental TFM system which was implemented using digital field memories and tested with a 10 m earth station operating through the COMSTAR D2 satellite. Received picture quality was excellent in all cases. Weighted SNR was 53-56 dB, and in practically all instances subjects could not tell any difference between single-picture FM transmission and TFM dual-picture transmission. View full abstract»

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  • A Terrestrial Rain Depolarization Compensation Experiment at 11.7 GHz

    Publication Year: 1983 , Page(s): 1241 - 1246
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    Depolarization caused by rain at 11.7 GHz is due to both differential phase shift and attenuation. In dual polarized communications systems it gives rise to interference which may be severe enough to cause an outage even though the allotted fade margin has not been exceeded. Described is a depolarization compensation experiment over a 10 km path with near circular polarization at 11.7 GHz. It made use of a turnstile junction feed system under computer control. Data presented demonstrate the stable performance of the method used during several rain events. At fades below about 15 dB significant isolation improvements were achieved, compared to a fixed cross-polarization channel. Finally, a method using the turnstile is suggested to receive two nonorthogonal signals without interference. View full abstract»

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  • A Double-Adaptive File Compression Algorithm

    Publication Year: 1983 , Page(s): 1253 - 1255
    Cited by:  Papers (16)  |  Patents (1)
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    We describe a one-pass compression scheme which presumes no statistical properties of the data being compressed. The model structure adaptively selects a subset of first-order Markov contexts, based on an estimate of the candidate context's popularity. The probability distributions for the unselected (lumped) first-order contexts are made the same, reducing cost over a full first-order Markov model. Symbol repetitions are handled in special secondorder Markov contexts. The statistics for each symbol are adaptively determined by an extension of earlier work. View full abstract»

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  • Optimum Discrete Pulse Shaping in MSK-Type Signals

    Publication Year: 1983 , Page(s): 1251 - 1253
    Cited by:  Papers (8)
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    We present in this correspondence a numerical approach to the problem of minimizing the fractional out-of-band power for a class of digital constant envelope modulated signals known as MSKtype signals. The present optimization procedure is much more manageable than a recently suggested analytical one while achieving the same results. View full abstract»

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  • Passive Arm Filters in I and Q Receivers for MSK-Type Continuous Phase Modulations

    Publication Year: 1983 , Page(s): 1235 - 1240
    Cited by:  Papers (2)
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    The use of Butterworth and Chebyshev low-pass filters in suboptimum in-phase ( I ) and quadrature phase ( Q ) receivers is considered for several bandwidth efficient modulations. These modulations are: minimum shift keying (MSK), tamed frequency modulation with rectangular pulse shaping (TFMREC), and MSK with duobinary encoding of the source bits (DMSK). The sensitivity of the modulations with their I and Q receivers to a noisy phase reference and to timing errors is also investigated. It was found that standard, passive low-pass filter receive filters performed quite well when compared to other nonstandard filters. The use of standard filters should thus be considered in any system design. The modulations, with their simple receivers, can be ranked in order of increasing sensitivity to timing errors as follows: MSK, DMSK, TFMREC. This ranking is the reverse to the one obtained when it is done in order of best bandwidth efficiency. View full abstract»

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  • Finite Population CSMA/CD Networks

    Publication Year: 1983 , Page(s): 1247 - 1251
    Cited by:  Papers (15)
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    A continuous time Markov chain model of a nonpersistent carrier sense multiple access with collision detection (CSMA/CD) protocol is developed to determine the performance of finite population systems. The model allows a wide range of distributions for the length of packets and the lengths of the transmission detection and collision detection times. A stability measure for finite population asynchronous systems-the instantaneous expected drift-is developed. Performance calculations for many sample systems show that the following behavior is characteristic of these systems: a wide range of retransmission rates provides almost optimal performance; the instantaneous drift is a sensitive indicator of the stability characteristics of CSMA/CD networks; if high fixed retransmission rates are used, performance decays very rapidly when other network parameters cross critical thresholds. In addition, adaptive retransmission policies and the maximum length of a CSMA/CD cable network are found to be very sensitive to the distribution of the transmission detection time. View full abstract»

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  • Differential Versus Limiter--Discriminator Detection of Narrow-Band FM

    Publication Year: 1983 , Page(s): 1227 - 1234
    Cited by:  Papers (70)  |  Patents (2)
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    The error probability performance of differential detection of narrow-band FM is determined and compared with the analogous results for limiter-discriminator detection of the same modulation. It is shown that over a large class of benign and hostile environments, e.g., Gaussian IF filter, 1 \leq BT \leq 3, h \leq 1 , AWGN, partial-band noise jamming, the differential detector offers no theoretical performance advantage over the limiter-discriminator receiver with integrate-and-dump postdetection filtering. View full abstract»

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  • On the Steady-State Distribution in a Service Facility Carrying Mixtures of Traffic with Different Peakedness Factors and Capacity Requirements

    Publication Year: 1983 , Page(s): 1209 - 1211
    Cited by:  Papers (27)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (248 KB)  

    A recursion formula is described. It is useful for calculating steady-state probabilities in a lost-call-cleared service facility carrying a mixture of message traffics with different peakedness factors and/or capacity requirements. In conjunction with the notion of equivalent trunk groups, these probabilities can then be used to evaluate the blocking probability perceived by each traffic stream. View full abstract»

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  • A Performance Model for Loss Systems with Crisis Calls

    Publication Year: 1983 , Page(s): 1212 - 1216
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    In this paper a mathematical model is developed for the performance of crisis calls. In such a system, a finite number of crisis calls attempt to use a communication link that has been receiving ordinary calls. The performance of the link with respect to the crisis calls is analyzed and studied. A numerical analysis is conducted to determine the behavior of the crisis calls under various scenarios. Some simple upper and lower bounds on the blocking and loss probabilities for crisis calls are given. View full abstract»

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  • The Performance of Digital Matched Filters for Multilevel Signals

    Publication Year: 1983 , Page(s): 1217 - 1226
    Cited by:  Papers (2)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (768 KB)  

    The analysis and optimization of digital matched filters (DMF's) with multilevel quantizers, which are matched to multilevel amplitude and phase modulated ( AM/\phi M ) signals, are considered here. Quite general expressions for the DMF's output signal-to-noise ratio (SNR0) have been obtained for the case in which the interference has a symmetric, differentiable probability density distribution. For such interference, SNR0has been shown to be separable into two factors, which respectively represent the effects of the quantization and correlation operations of the DMF. The two factors can be optimized independently of each other. In particular, the optimal quantizer strategy for Gaussian interference is proven to be (within the limits of practical approximation and also asymptotically) one with equal spacings of the quantizer levels and thresholds. All the SNR0calculations have been carried out for a complex output X rather than the commonly used real-valued, physical output Z . The validity of the relationship SNR_{0}X = 2 SNR_{0}Z has been proven for all types of interference considered in this work. Finally, the optimal SNR_{0}X for Gaussian interference has been proven to be bounded from above by SNR_{0}X for the analog matched filter and from below by that of DMF with hard limiter as a quantizer. 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